691811640 has 288 divisors, whose sum is σ = 2481963120. Its totient is φ = 167012352.

The previous prime is 691811633. The next prime is 691811647. The reversal of 691811640 is 46118196.

It is a happy number.

691811640 is a `hidden beast` number, since 6 + 9 + 1 + 8 + 1 + 1 + 640 = 666.

It is an interprime number because it is at equal distance from previous prime (691811633) and next prime (691811647).

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 691811595 and 691811604.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (691811647) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 5049652 + ... + 5049788.

Almost surely, 2^691811640 is an apocalyptic number.

691811640 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 691811640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1240981560).

691811640 is an abundant number, since it is smaller than the sum of its proper divisors (1790151480).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

691811640 is a wasteful number, since it uses less digits than its factorization.

691811640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 263 (or 243 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 36.

The square root of 691811640 is about 26302.3124458668. The cubic root of 691811640 is about 884.4282815148.

The spelling of 691811640 in words is "six hundred ninety-one million, eight hundred eleven thousand, six hundred forty".