691087657 has 4 divisors (see below), whose sum is σ = 744248260. Its totient is φ = 637927056.

The previous prime is 691087651. The next prime is 691087687. The reversal of 691087657 is 756780196.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 401441296 + 289646361 = 20036^2 + 17019^2 .

It is not a de Polignac number, because 691087657 - 2¹¹ = 691085609 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 691087657.

It is not an unprimeable number, because it can be changed into a prime (691087651) 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, 26580282 + ... + 26580307.

It is an arithmetic number, because the mean of its divisors is an integer number (186062065).

Almost surely, 2^691087657 is an apocalyptic number.

It is an amenable number.

691087657 is a deficient number, since it is larger than the sum of its proper divisors (53160603).

691087657 is a wasteful number, since it uses less digits than its factorization.

691087657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53160602.

The product of its (nonzero) digits is 635040, while the sum is 49.

The square root of 691087657 is about 26288.5461180340. The cubic root of 691087657 is about 884.1196548617.

The spelling of 691087657 in words is "six hundred ninety-one million, eighty-seven thousand, six hundred fifty-seven".