21621351566531 has 8 divisors (see below), whose sum is σ = 21640779072000. Its totient is φ = 21601928662600.

The previous prime is 21621351566491. The next prime is 21621351566543. The reversal of 21621351566531 is 13566515312612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21621351566531 - 2¹⁸ = 21621351304387 is a prime.

It is a super-2 number, since 2×21621351566531² (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 (21621351566431) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8286020 + ... + 10578318.

It is an arithmetic number, because the mean of its divisors is an integer number (2705097384000).

Almost surely, 2^{21621351566531} is an apocalyptic number.

21621351566531 is a deficient number, since it is larger than the sum of its proper divisors (19427505469).

21621351566531 is a wasteful number, since it uses less digits than its factorization.

21621351566531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2300769.

The product of its digits is 972000, while the sum is 47.

The spelling of 21621351566531 in words is "twenty-one trillion, six hundred twenty-one billion, three hundred fifty-one million, five hundred sixty-six thousand, five hundred thirty-one".