691365780 has 240 divisors, whose sum is σ = 2540837376. Its totient is φ = 154068480.

The previous prime is 691365743. The next prime is 691365781. The reversal of 691365780 is 87563196.

It is a happy number.

691365780 is a `hidden beast` number, since 69 + 13 + 6 + 578 + 0 = 666.

691365780 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (691365781) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 464197 + ... + 465683.

Almost surely, 2^691365780 is an apocalyptic number.

691365780 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 691365780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1270418688).

691365780 is an abundant number, since it is smaller than the sum of its proper divisors (1849471596).

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

691365780 is a wasteful number, since it uses less digits than its factorization.

691365780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1556 (or 1545 counting only the distinct ones).

The product of its (nonzero) digits is 272160, while the sum is 45.

The square root of 691365780 is about 26293.8353991958. The cubic root of 691365780 is about 884.2382413775.

The spelling of 691365780 in words is "six hundred ninety-one million, three hundred sixty-five thousand, seven hundred eighty".