20880721 has 2 divisors, whose sum is σ = 20880722. Its totient is φ = 20880720.

The previous prime is 20880697. The next prime is 20880731. The reversal of 20880721 is 12708802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20830096 + 50625 = 4564^2 + 225^2 .

It is a cyclic number.

It is not a de Polignac number, because 20880721 - 2⁵ = 20880689 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20880721.

It is not a weakly prime, because it can be changed into another prime (20880731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10440360 + 10440361.

It is an arithmetic number, because the mean of its divisors is an integer number (10440361).

Almost surely, 2^20880721 is an apocalyptic number.

It is an amenable number.

20880721 is a deficient number, since it is larger than the sum of its proper divisors (1).

20880721 is an equidigital number, since it uses as much as digits as its factorization.

20880721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1792, while the sum is 28.

The square root of 20880721 is about 4569.5427561190. The cubic root of 20880721 is about 275.3690735960.

The spelling of 20880721 in words is "twenty million, eight hundred eighty thousand, seven hundred twenty-one".