15700721 has 4 divisors (see below), whose sum is σ = 15775344. Its totient is φ = 15626100.

The previous prime is 15700717. The next prime is 15700739. The reversal of 15700721 is 12700751.

It is a happy number.

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 15700721 - 2² = 15700717 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15700771) 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, 36995 + ... + 37416.

It is an arithmetic number, because the mean of its divisors is an integer number (3943836).

Almost surely, 2^15700721 is an apocalyptic number.

It is an amenable number.

15700721 is a deficient number, since it is larger than the sum of its proper divisors (74623).

15700721 is an equidigital number, since it uses as much as digits as its factorization.

15700721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74622.

The product of its (nonzero) digits is 490, while the sum is 23.

The square root of 15700721 is about 3962.4135321796. The cubic root of 15700721 is about 250.4031947198.

The spelling of 15700721 in words is "fifteen million, seven hundred thousand, seven hundred twenty-one".