20922721 has 2 divisors, whose sum is σ = 20922722. Its totient is φ = 20922720.

The previous prime is 20922703. The next prime is 20922731. The reversal of 20922721 is 12722902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19018321 + 1904400 = 4361^2 + 1380^2 .

It is a cyclic number.

It is not a de Polignac number, because 20922721 - 2¹¹ = 20920673 is a prime.

It is not a weakly prime, because it can be changed into another prime (20922731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10461360 + 10461361.

It is an arithmetic number, because the mean of its divisors is an integer number (10461361).

Almost surely, 2^20922721 is an apocalyptic number.

It is an amenable number.

20922721 is a deficient number, since it is larger than the sum of its proper divisors (1).

20922721 is an equidigital number, since it uses as much as digits as its factorization.

20922721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1008, while the sum is 25.

The square root of 20922721 is about 4574.1360932967. The cubic root of 20922721 is about 275.5535780066.

The spelling of 20922721 in words is "twenty million, nine hundred twenty-two thousand, seven hundred twenty-one".