21531204523251 has 24 divisors (see below), whose sum is σ = 32110187925504. Its totient is φ = 13888368071280.

The previous prime is 21531204523249. The next prime is 21531204523261. The reversal of 21531204523251 is 15232540213512.

21531204523251 is a `hidden beast` number, since 2 + 1 + 5 + 3 + 120 + 4 + 523 + 2 + 5 + 1 = 666.

It is not a de Polignac number, because 21531204523251 - 2¹ = 21531204523249 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21531204523211) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 6166021 + ... + 9004566.

It is an arithmetic number, because the mean of its divisors is an integer number (1337924496896).

Almost surely, 2^{21531204523251} is an apocalyptic number.

21531204523251 is a deficient number, since it is larger than the sum of its proper divisors (10578983402253).

21531204523251 is a wasteful number, since it uses less digits than its factorization.

21531204523251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15175711 (or 15175708 counting only the distinct ones).

The product of its (nonzero) digits is 72000, while the sum is 36.

Adding to 21531204523251 its reverse (15232540213512), we get a palindrome (36763744736763).

The spelling of 21531204523251 in words is "twenty-one trillion, five hundred thirty-one billion, two hundred four million, five hundred twenty-three thousand, two hundred fifty-one".