21215452564021 has 2 divisors, whose sum is σ = 21215452564022. Its totient is φ = 21215452564020.

The previous prime is 21215452564003. The next prime is 21215452564091. The reversal of 21215452564021 is 12046525451212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14217914542225 + 6997538021796 = 3770665^2 + 2645286^2 .

It is a cyclic number.

It is not a de Polignac number, because 21215452564021 - 2⁹ = 21215452563509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21215452564091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10607726282010 + 10607726282011.

It is an arithmetic number, because the mean of its divisors is an integer number (10607726282011).

Almost surely, 2^{21215452564021} is an apocalyptic number.

It is an amenable number.

21215452564021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21215452564021 is an equidigital number, since it uses as much as digits as its factorization.

21215452564021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 192000, while the sum is 40.

The spelling of 21215452564021 in words is "twenty-one trillion, two hundred fifteen billion, four hundred fifty-two million, five hundred sixty-four thousand, twenty-one".