21501512321521 has 16 divisors (see below), whose sum is σ = 21569846120064. Its totient is φ = 21433307108224.

The previous prime is 21501512321507. The next prime is 21501512321557. The reversal of 21501512321521 is 12512321510512.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21501512321521 is a prime.

It is a super-2 number, since 2×21501512321521² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21501512321591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1282668486 + ... + 1282685248.

It is an arithmetic number, because the mean of its divisors is an integer number (1348115382504).

Almost surely, 2^{21501512321521} is an apocalyptic number.

It is an amenable number.

21501512321521 is a deficient number, since it is larger than the sum of its proper divisors (68333798543).

21501512321521 is a wasteful number, since it uses less digits than its factorization.

21501512321521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20360.

The product of its (nonzero) digits is 6000, while the sum is 31.

The spelling of 21501512321521 in words is "twenty-one trillion, five hundred one billion, five hundred twelve million, three hundred twenty-one thousand, five hundred twenty-one".