21625621 has 2 divisors, whose sum is σ = 21625622. Its totient is φ = 21625620.

The previous prime is 21625607. The next prime is 21625633. The reversal of 21625621 is 12652612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14938225 + 6687396 = 3865^2 + 2586^2 .

It is a cyclic number.

It is not a de Polignac number, because 21625621 - 2¹⁵ = 21592853 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21625661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10812810 + 10812811.

It is an arithmetic number, because the mean of its divisors is an integer number (10812811).

Almost surely, 2^21625621 is an apocalyptic number.

It is an amenable number.

21625621 is a deficient number, since it is larger than the sum of its proper divisors (1).

21625621 is an equidigital number, since it uses as much as digits as its factorization.

21625621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1440, while the sum is 25.

The square root of 21625621 is about 4650.3355792889. The cubic root of 21625621 is about 278.6053996078.

The spelling of 21625621 in words is "twenty-one million, six hundred twenty-five thousand, six hundred twenty-one".