21525945521 has 2 divisors, whose sum is σ = 21525945522. Its totient is φ = 21525945520.

The previous prime is 21525945499. The next prime is 21525945587. The reversal of 21525945521 is 12554952512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21019200400 + 506745121 = 144980^2 + 22511^2 .

It is a cyclic number.

It is not a de Polignac number, because 21525945521 - 2²² = 21521751217 is a prime.

It is a super-2 number, since 2×21525945521² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21525945421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10762972760 + 10762972761.

It is an arithmetic number, because the mean of its divisors is an integer number (10762972761).

Almost surely, 2^21525945521 is an apocalyptic number.

It is an amenable number.

21525945521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21525945521 is an equidigital number, since it uses as much as digits as its factorization.

21525945521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 180000, while the sum is 41.

The spelling of 21525945521 in words is "twenty-one billion, five hundred twenty-five million, nine hundred forty-five thousand, five hundred twenty-one".