21620542645057 has 2 divisors, whose sum is σ = 21620542645058. Its totient is φ = 21620542645056.

The previous prime is 21620542645007. The next prime is 21620542645171. The reversal of 21620542645057 is 75054624502612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15088843038096 + 6531699606961 = 3884436^2 + 2555719^2 .

It is a cyclic number.

It is not a de Polignac number, because 21620542645057 - 2¹¹ = 21620542643009 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21620542645057.

It is not a weakly prime, because it can be changed into another prime (21620542645007) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10810271322528 + 10810271322529.

It is an arithmetic number, because the mean of its divisors is an integer number (10810271322529).

Almost surely, 2^{21620542645057} is an apocalyptic number.

It is an amenable number.

21620542645057 is a deficient number, since it is larger than the sum of its proper divisors (1).

21620542645057 is an equidigital number, since it uses as much as digits as its factorization.

21620542645057 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4032000, while the sum is 49.

The spelling of 21620542645057 in words is "twenty-one trillion, six hundred twenty billion, five hundred forty-two million, six hundred forty-five thousand, fifty-seven".