691557966 has 64 divisors (see below), whose sum is σ = 1691504640. Its totient is φ = 207688320.

The previous prime is 691557941. The next prime is 691557967. The reversal of 691557966 is 669755196.

691557966 is a `hidden beast` number, since 6 + 9 + 1 + 5 + 579 + 66 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (691557967) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 61971 + ... + 72273.

It is an arithmetic number, because the mean of its divisors is an integer number (26429760).

Almost surely, 2^691557966 is an apocalyptic number.

691557966 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 691557966, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (845752320).

691557966 is an abundant number, since it is smaller than the sum of its proper divisors (999946674).

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

691557966 is a wasteful number, since it uses less digits than its factorization.

691557966 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10438 (or 10432 counting only the distinct ones).

The product of its digits is 3061800, while the sum is 54.

The square root of 691557966 is about 26297.4897281090. The cubic root of 691557966 is about 884.3201673621.

The spelling of 691557966 in words is "six hundred ninety-one million, five hundred fifty-seven thousand, nine hundred sixty-six".