691216057 has 4 divisors (see below), whose sum is σ = 789961216. Its totient is φ = 592470900.

The previous prime is 691216037. The next prime is 691216069. The reversal of 691216057 is 750612196.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a de Polignac number, because none of the positive numbers 2^k-691216057 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (691216037) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 49372569 + ... + 49372582.

It is an arithmetic number, because the mean of its divisors is an integer number (197490304).

Almost surely, 2^691216057 is an apocalyptic number.

It is an amenable number.

691216057 is a deficient number, since it is larger than the sum of its proper divisors (98745159).

691216057 is an equidigital number, since it uses as much as digits as its factorization.

691216057 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 98745158.

The product of its (nonzero) digits is 22680, while the sum is 37.

The square root of 691216057 is about 26290.9881328184. The cubic root of 691216057 is about 884.1744062056.

The spelling of 691216057 in words is "six hundred ninety-one million, two hundred sixteen thousand, fifty-seven".