20691657 has 12 divisors (see below), whose sum is σ = 34157760. Its totient is φ = 11823768.

The previous prime is 20691653. The next prime is 20691659. The reversal of 20691657 is 75619602.

It is not a de Polignac number, because 20691657 - 2² = 20691653 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20691653) 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, 164157 + ... + 164282.

It is an arithmetic number, because the mean of its divisors is an integer number (2846480).

Almost surely, 2^20691657 is an apocalyptic number.

It is an amenable number.

20691657 is a deficient number, since it is larger than the sum of its proper divisors (13466103).

20691657 is a wasteful number, since it uses less digits than its factorization.

20691657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 328452 (or 328449 counting only the distinct ones).

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

The square root of 20691657 is about 4548.8083054796. The cubic root of 20691657 is about 274.5354448740.

The spelling of 20691657 in words is "twenty million, six hundred ninety-one thousand, six hundred fifty-seven".