15399721 has 2 divisors, whose sum is σ = 15399722. Its totient is φ = 15399720.

The previous prime is 15399701. The next prime is 15399763. The reversal of 15399721 is 12799351.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14930496 + 469225 = 3864^2 + 685^2 .

It is a cyclic number.

It is not a de Polignac number, because 15399721 - 2⁵ = 15399689 is a prime.

It is not a weakly prime, because it can be changed into another prime (15399701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7699860 + 7699861.

It is an arithmetic number, because the mean of its divisors is an integer number (7699861).

Almost surely, 2^15399721 is an apocalyptic number.

It is an amenable number.

15399721 is a deficient number, since it is larger than the sum of its proper divisors (1).

15399721 is an equidigital number, since it uses as much as digits as its factorization.

15399721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 17010, while the sum is 37.

The square root of 15399721 is about 3924.2478260171. The cubic root of 15399721 is about 248.7926910054.

The spelling of 15399721 in words is "fifteen million, three hundred ninety-nine thousand, seven hundred twenty-one".