20657691 has 12 divisors (see below), whose sum is σ = 29878368. Its totient is φ = 13753584.

The previous prime is 20657677. The next prime is 20657699. The reversal of 20657691 is 19675602.

It is not a de Polignac number, because 20657691 - 2⁶ = 20657627 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20657699) 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, 12001 + ... + 13613.

It is an arithmetic number, because the mean of its divisors is an integer number (2489864).

Almost surely, 2^20657691 is an apocalyptic number.

20657691 is a deficient number, since it is larger than the sum of its proper divisors (9220677).

20657691 is a wasteful number, since it uses less digits than its factorization.

20657691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3042 (or 3039 counting only the distinct ones).

The product of its (nonzero) digits is 22680, while the sum is 36.

The square root of 20657691 is about 4545.0732667362. The cubic root of 20657691 is about 274.3851431053.

The spelling of 20657691 in words is "twenty million, six hundred fifty-seven thousand, six hundred ninety-one".