15969721 has 2 divisors, whose sum is σ = 15969722. Its totient is φ = 15969720.

The previous prime is 15969713. The next prime is 15969731. The reversal of 15969721 is 12796951.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15912121 + 57600 = 3989^2 + 240^2 .

It is a cyclic number.

It is not a de Polignac number, because 15969721 - 2³ = 15969713 is a prime.

It is not a weakly prime, because it can be changed into another prime (15969731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7984860 + 7984861.

It is an arithmetic number, because the mean of its divisors is an integer number (7984861).

Almost surely, 2^15969721 is an apocalyptic number.

It is an amenable number.

15969721 is a deficient number, since it is larger than the sum of its proper divisors (1).

15969721 is an equidigital number, since it uses as much as digits as its factorization.

15969721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 34020, while the sum is 40.

The square root of 15969721 is about 3996.2133326438. The cubic root of 15969721 is about 251.8251548133.

The spelling of 15969721 in words is "fifteen million, nine hundred sixty-nine thousand, seven hundred twenty-one".