20905657 has 2 divisors, whose sum is σ = 20905658. Its totient is φ = 20905656.

The previous prime is 20905637. The next prime is 20905663. The reversal of 20905657 is 75650902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19395216 + 1510441 = 4404^2 + 1229^2 .

It is a cyclic number.

It is not a de Polignac number, because 20905657 - 2¹⁹ = 20381369 is a prime.

It is not a weakly prime, because it can be changed into another prime (20905627) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10452828 + 10452829.

It is an arithmetic number, because the mean of its divisors is an integer number (10452829).

Almost surely, 2^20905657 is an apocalyptic number.

It is an amenable number.

20905657 is a deficient number, since it is larger than the sum of its proper divisors (1).

20905657 is an equidigital number, since it uses as much as digits as its factorization.

20905657 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 18900, while the sum is 34.

The square root of 20905657 is about 4572.2704425701. The cubic root of 20905657 is about 275.4786463072.

The spelling of 20905657 in words is "twenty million, nine hundred five thousand, six hundred fifty-seven".