21005627621 has 32 divisors (see below), whose sum is σ = 24314314752. Its totient is φ = 17967600000.

The previous prime is 21005627537. The next prime is 21005627647. The reversal of 21005627621 is 12672650012.

It is not a de Polignac number, because 21005627621 - 2¹⁰ = 21005626597 is a prime.

It is a Smith number, since the sum of its digits (32) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21005627221) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4345676 + ... + 4350506.

It is an arithmetic number, because the mean of its divisors is an integer number (759822336).

Almost surely, 2^21005627621 is an apocalyptic number.

It is an amenable number.

21005627621 is a deficient number, since it is larger than the sum of its proper divisors (3308687131).

21005627621 is a wasteful number, since it uses less digits than its factorization.

21005627621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5225.

The product of its (nonzero) digits is 10080, while the sum is 32.

The spelling of 21005627621 in words is "twenty-one billion, five million, six hundred twenty-seven thousand, six hundred twenty-one".