15721457 has 4 divisors (see below), whose sum is σ = 15845376. Its totient is φ = 15597540.

The previous prime is 15721439. The next prime is 15721463. The reversal of 15721457 is 75412751.

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 15721457 - 2¹⁴ = 15705073 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15721427) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 61769 + ... + 62022.

It is an arithmetic number, because the mean of its divisors is an integer number (3961344).

Almost surely, 2^15721457 is an apocalyptic number.

It is an amenable number.

15721457 is a deficient number, since it is larger than the sum of its proper divisors (123919).

15721457 is a wasteful number, since it uses less digits than its factorization.

15721457 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 123918.

The product of its digits is 9800, while the sum is 32.

The square root of 15721457 is about 3965.0292558820. The cubic root of 15721457 is about 250.5133823659.

The spelling of 15721457 in words is "fifteen million, seven hundred twenty-one thousand, four hundred fifty-seven".