21213600255621 has 12 divisors (see below), whose sum is σ = 30656792472748. Its totient is φ = 14135511507264.

The previous prime is 21213600255487. The next prime is 21213600255629. The reversal of 21213600255621 is 12655200631212.

21213600255621 is a `hidden beast` number, since 2 + 1 + 2 + 1 + 3 + 6 + 0 + 0 + 25 + 5 + 621 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 16268202624996 + 4945397630625 = 4033386^2 + 2223825^2 .

It is not a de Polignac number, because 21213600255621 - 2¹⁰ = 21213600254597 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21213600255629) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 574035760 + ... + 574072713.

Almost surely, 2^{21213600255621} is an apocalyptic number.

It is an amenable number.

21213600255621 is a deficient number, since it is larger than the sum of its proper divisors (9443192217127).

21213600255621 is a wasteful number, since it uses less digits than its factorization.

21213600255621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1148110532 (or 1148110529 counting only the distinct ones).

The product of its (nonzero) digits is 43200, while the sum is 36.

Adding to 21213600255621 its reverse (12655200631212), we get a palindrome (33868800886833).

The spelling of 21213600255621 in words is "twenty-one trillion, two hundred thirteen billion, six hundred million, two hundred fifty-five thousand, six hundred twenty-one".