21254002561021 has 4 divisors (see below), whose sum is σ = 21464438230044. Its totient is φ = 21043566892000.

The previous prime is 21254002561019. The next prime is 21254002561027. The reversal of 21254002561021 is 12016520045212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 16702547265625 + 4551455295396 = 4086875^2 + 2133414^2 .

It is a cyclic number.

It is not a de Polignac number, because 21254002561021 - 2¹ = 21254002561019 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21254002561027) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 105217834360 + ... + 105217834561.

It is an arithmetic number, because the mean of its divisors is an integer number (5366109557511).

Almost surely, 2^{21254002561021} is an apocalyptic number.

It is an amenable number.

21254002561021 is a deficient number, since it is larger than the sum of its proper divisors (210435669023).

21254002561021 is a wasteful number, since it uses less digits than its factorization.

21254002561021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 210435669022.

The product of its (nonzero) digits is 9600, while the sum is 31.

The spelling of 21254002561021 in words is "twenty-one trillion, two hundred fifty-four billion, two million, five hundred sixty-one thousand, twenty-one".