21620522180581 has 8 divisors (see below), whose sum is σ = 22206017068664. Its totient is φ = 21035088158400.

The previous prime is 21620522180573. The next prime is 21620522180611. The reversal of 21620522180581 is 18508122502612.

It can be written as a sum of positive squares in 4 ways, for example, as 14232095777025 + 7388426403556 = 3772545^2 + 2718166^2 .

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 21620522180581 - 2³ = 21620522180573 is a prime.

It is a super-2 number, since 2×21620522180581² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21620522180561) 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, 14495970 + ... + 15917731.

It is an arithmetic number, because the mean of its divisors is an integer number (2775752133583).

Almost surely, 2^{21620522180581} is an apocalyptic number.

It is an amenable number.

21620522180581 is a deficient number, since it is larger than the sum of its proper divisors (585494888083).

21620522180581 is a wasteful number, since it uses less digits than its factorization.

21620522180581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30432951.

The product of its (nonzero) digits is 153600, while the sum is 43.

The spelling of 21620522180581 in words is "twenty-one trillion, six hundred twenty billion, five hundred twenty-two million, one hundred eighty thousand, five hundred eighty-one".