21192521621 has 2 divisors, whose sum is σ = 21192521622. Its totient is φ = 21192521620.

The previous prime is 21192521531. The next prime is 21192521641. The reversal of 21192521621 is 12612529112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13729980625 + 7462540996 = 117175^2 + 86386^2 .

It is a cyclic number.

It is not a de Polignac number, because 21192521621 - 2¹⁸ = 21192259477 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21192521641) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10596260810 + 10596260811.

It is an arithmetic number, because the mean of its divisors is an integer number (10596260811).

Almost surely, 2^21192521621 is an apocalyptic number.

It is an amenable number.

21192521621 is a deficient number, since it is larger than the sum of its proper divisors (1).

21192521621 is an equidigital number, since it uses as much as digits as its factorization.

21192521621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4320, while the sum is 32.

The spelling of 21192521621 in words is "twenty-one billion, one hundred ninety-two million, five hundred twenty-one thousand, six hundred twenty-one".