15940721 has 2 divisors, whose sum is σ = 15940722. Its totient is φ = 15940720.

The previous prime is 15940697. The next prime is 15940723. The reversal of 15940721 is 12704951.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14145121 + 1795600 = 3761^2 + 1340^2 .

It is a cyclic number.

It is not a de Polignac number, because 15940721 - 2⁶ = 15940657 is a prime.

Together with 15940723, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (15940723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7970360 + 7970361.

It is an arithmetic number, because the mean of its divisors is an integer number (7970361).

Almost surely, 2^15940721 is an apocalyptic number.

It is an amenable number.

15940721 is a deficient number, since it is larger than the sum of its proper divisors (1).

15940721 is an equidigital number, since it uses as much as digits as its factorization.

15940721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2520, while the sum is 29.

The square root of 15940721 is about 3992.5832489755. The cubic root of 15940721 is about 251.6726296167.

It can be divided in two parts, 15940 and 721, that added together give a palindrome (16661).

The spelling of 15940721 in words is "fifteen million, nine hundred forty thousand, seven hundred twenty-one".