15640691 has 12 divisors (see below), whose sum is σ = 17491320. Its totient is φ = 13870080.

The previous prime is 15640687. The next prime is 15640693. The reversal of 15640691 is 19604651.

It is not a de Polignac number, because 15640691 - 2² = 15640687 is a prime.

It is a nialpdrome in base 16.

It is not an unprimeable number, because it can be changed into a prime (15640693) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 19955 + ... + 20723.

It is an arithmetic number, because the mean of its divisors is an integer number (1457610).

Almost surely, 2^15640691 is an apocalyptic number.

15640691 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

15640691 is a deficient number, since it is larger than the sum of its proper divisors (1850629).

15640691 is an equidigital number, since it uses as much as digits as its factorization.

15640691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 866 (or 823 counting only the distinct ones).

The product of its (nonzero) digits is 6480, while the sum is 32.

The square root of 15640691 is about 3954.8313491222. The cubic root of 15640691 is about 250.0836573360.

The spelling of 15640691 in words is "fifteen million, six hundred forty thousand, six hundred ninety-one".