20815871957 has 2 divisors, whose sum is σ = 20815871958. Its totient is φ = 20815871956.

The previous prime is 20815871939. The next prime is 20815872001. The reversal of 20815871957 is 75917851802.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14960714596 + 5855157361 = 122314^2 + 76519^2 .

It is a cyclic number.

It is not a de Polignac number, because 20815871957 - 2⁶ = 20815871893 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20815871899 and 20815871908.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20815871917) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10407935978 + 10407935979.

It is an arithmetic number, because the mean of its divisors is an integer number (10407935979).

Almost surely, 2^20815871957 is an apocalyptic number.

It is an amenable number.

20815871957 is a deficient number, since it is larger than the sum of its proper divisors (1).

20815871957 is an equidigital number, since it uses as much as digits as its factorization.

20815871957 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1411200, while the sum is 53.

The spelling of 20815871957 in words is "twenty billion, eight hundred fifteen million, eight hundred seventy-one thousand, nine hundred fifty-seven".