21666739538925 has 768 divisors, whose sum is σ = 49993600204800. Its totient is φ = 9079182950400.

The previous prime is 21666739538881. The next prime is 21666739538947. The reversal of 21666739538925 is 52983593766612.

It is not a de Polignac number, because 21666739538925 - 2⁸ = 21666739538669 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 767 ways as a sum of consecutive naturals, for example, 5461742292 + ... + 5461746258.

It is an arithmetic number, because the mean of its divisors is an integer number (65095833600).

Almost surely, 2^{21666739538925} is an apocalyptic number.

21666739538925 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21666739538925 is an abundant number, since it is smaller than the sum of its proper divisors (28326860665875).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21666739538925 is a wasteful number, since it uses less digits than its factorization.

21666739538925 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4123 (or 4112 counting only the distinct ones).

The product of its digits is 881798400, while the sum is 72.

The spelling of 21666739538925 in words is "twenty-one trillion, six hundred sixty-six billion, seven hundred thirty-nine million, five hundred thirty-eight thousand, nine hundred twenty-five".