21525512381 has 2 divisors, whose sum is σ = 21525512382. Its totient is φ = 21525512380.

The previous prime is 21525512369. The next prime is 21525512383. The reversal of 21525512381 is 18321552512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16375297156 + 5150215225 = 127966^2 + 71765^2 .

It is a cyclic number.

It is not a de Polignac number, because 21525512381 - 2³⁰ = 20451770557 is a prime.

It is a super-2 number, since 2×21525512381² (a number of 21 digits) contains 22 as substring.

It is a Sophie Germain prime.

Together with 21525512383, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21525512383) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10762756190 + 10762756191.

It is an arithmetic number, because the mean of its divisors is an integer number (10762756191).

Almost surely, 2^21525512381 is an apocalyptic number.

It is an amenable number.

21525512381 is a deficient number, since it is larger than the sum of its proper divisors (1).

21525512381 is an equidigital number, since it uses as much as digits as its factorization.

21525512381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 24000, while the sum is 35.

The spelling of 21525512381 in words is "twenty-one billion, five hundred twenty-five million, five hundred twelve thousand, three hundred eighty-one".