15916721 has 4 divisors (see below), whose sum is σ = 16154352. Its totient is φ = 15679092.

The previous prime is 15916711. The next prime is 15916723. The reversal of 15916721 is 12761951.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 15916721 - 2⁶ = 15916657 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15916723) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 118715 + ... + 118848.

It is an arithmetic number, because the mean of its divisors is an integer number (4038588).

Almost surely, 2^15916721 is an apocalyptic number.

It is an amenable number.

15916721 is a deficient number, since it is larger than the sum of its proper divisors (237631).

15916721 is an equidigital number, since it uses as much as digits as its factorization.

15916721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 237630.

The product of its digits is 3780, while the sum is 32.

The square root of 15916721 is about 3989.5765439455. The cubic root of 15916721 is about 251.5462619124.

The spelling of 15916721 in words is "fifteen million, nine hundred sixteen thousand, seven hundred twenty-one".