21621566454157 has 4 divisors (see below), whose sum is σ = 21627584149500. Its totient is φ = 21615548758816.

The previous prime is 21621566454149. The next prime is 21621566454167. The reversal of 21621566454157 is 75145466512612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 6085403193321 + 15536163260836 = 2466861^2 + 3941594^2 .

It is a cyclic number.

It is not a de Polignac number, because 21621566454157 - 2³ = 21621566454149 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21621566454098 and 21621566454107.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21621566454107) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3008842282 + ... + 3008849467.

It is an arithmetic number, because the mean of its divisors is an integer number (5406896037375).

Almost surely, 2^{21621566454157} is an apocalyptic number.

It is an amenable number.

21621566454157 is a deficient number, since it is larger than the sum of its proper divisors (6017695343).

21621566454157 is an equidigital number, since it uses as much as digits as its factorization.

21621566454157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6017695342.

The product of its digits is 12096000, while the sum is 55.

The spelling of 21621566454157 in words is "twenty-one trillion, six hundred twenty-one billion, five hundred sixty-six million, four hundred fifty-four thousand, one hundred fifty-seven".