21015244457 has 2 divisors, whose sum is σ = 21015244458. Its totient is φ = 21015244456.

The previous prime is 21015244421. The next prime is 21015244513. The reversal of 21015244457 is 75444251012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17649388201 + 3365856256 = 132851^2 + 58016^2 .

It is a cyclic number.

It is not a de Polignac number, because 21015244457 - 2²⁸ = 20746809001 is a prime.

It is not a weakly prime, because it can be changed into another prime (21015244057) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10507622228 + 10507622229.

It is an arithmetic number, because the mean of its divisors is an integer number (10507622229).

Almost surely, 2^21015244457 is an apocalyptic number.

It is an amenable number.

21015244457 is a deficient number, since it is larger than the sum of its proper divisors (1).

21015244457 is an equidigital number, since it uses as much as digits as its factorization.

21015244457 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 44800, while the sum is 35.

Adding to 21015244457 its reverse (75444251012), we get a palindrome (96459495469).

The spelling of 21015244457 in words is "twenty-one billion, fifteen million, two hundred forty-four thousand, four hundred fifty-seven".