21666624650525 has 6 divisors (see below), whose sum is σ = 26866614566682. Its totient is φ = 17333299720400.

The previous prime is 21666624650509. The next prime is 21666624650543. The reversal of 21666624650525 is 52505642666612.

It can be written as a sum of positive squares in 3 ways, for example, as 6512841808729 + 15153782841796 = 2552027^2 + 3892786^2 .

It is not a de Polignac number, because 21666624650525 - 2⁴ = 21666624650509 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 433332492986 + ... + 433332493035.

It is an arithmetic number, because the mean of its divisors is an integer number (4477769094447).

Almost surely, 2^{21666624650525} is an apocalyptic number.

21666624650525 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21666624650525 is a deficient number, since it is larger than the sum of its proper divisors (5199989916157).

21666624650525 is an equidigital number, since it uses as much as digits as its factorization.

21666624650525 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 866664986031 (or 866664986026 counting only the distinct ones).

The product of its (nonzero) digits is 31104000, while the sum is 56.

The spelling of 21666624650525 in words is "twenty-one trillion, six hundred sixty-six billion, six hundred twenty-four million, six hundred fifty thousand, five hundred twenty-five".