13920721 has 2 divisors, whose sum is σ = 13920722. Its totient is φ = 13920720.

The previous prime is 13920713. The next prime is 13920737. The reversal of 13920721 is 12702931.

13920721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11296321 + 2624400 = 3361^2 + 1620^2 .

It is a cyclic number.

It is not a de Polignac number, because 13920721 - 2³ = 13920713 is a prime.

It is not a weakly prime, because it can be changed into another prime (13924721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6960360 + 6960361.

It is an arithmetic number, because the mean of its divisors is an integer number (6960361).

Almost surely, 2^13920721 is an apocalyptic number.

It is an amenable number.

13920721 is a deficient number, since it is larger than the sum of its proper divisors (1).

13920721 is an equidigital number, since it uses as much as digits as its factorization.

13920721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 756, while the sum is 25.

The square root of 13920721 is about 3731.0482441266. The cubic root of 13920721 is about 240.5584276621.

It can be divided in two parts, 13920 and 721, that added together give a palindrome (14641).

The spelling of 13920721 in words is "thirteen million, nine hundred twenty thousand, seven hundred twenty-one".