21506672142521 has 4 divisors (see below), whose sum is σ = 21506686656000. Its totient is φ = 21506657629044.

The previous prime is 21506672142511. The next prime is 21506672142541. The reversal of 21506672142521 is 12524127660512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21506672142521 - 2²⁶ = 21506605033657 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21506672142511) 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, 4743941 + ... + 8094338.

It is an arithmetic number, because the mean of its divisors is an integer number (5376671664000).

Almost surely, 2^{21506672142521} is an apocalyptic number.

It is an amenable number.

21506672142521 is a deficient number, since it is larger than the sum of its proper divisors (14513479).

21506672142521 is a wasteful number, since it uses less digits than its factorization.

21506672142521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14513478.

The product of its (nonzero) digits is 403200, while the sum is 44.

The spelling of 21506672142521 in words is "twenty-one trillion, five hundred six billion, six hundred seventy-two million, one hundred forty-two thousand, five hundred twenty-one".