15813921 has 4 divisors (see below), whose sum is σ = 21085232. Its totient is φ = 10542612.

The previous prime is 15813887. The next prime is 15813923. The reversal of 15813921 is 12931851.

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 not a de Polignac number, because 15813921 - 2⁷ = 15813793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15813923) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2635651 + ... + 2635656.

It is an arithmetic number, because the mean of its divisors is an integer number (5271308).

Almost surely, 2^15813921 is an apocalyptic number.

It is an amenable number.

15813921 is a deficient number, since it is larger than the sum of its proper divisors (5271311).

15813921 is an equidigital number, since it uses as much as digits as its factorization.

15813921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5271310.

The product of its digits is 2160, while the sum is 30.

The square root of 15813921 is about 3976.6721011419. The cubic root of 15813921 is about 251.0035448672.

The spelling of 15813921 in words is "fifteen million, eight hundred thirteen thousand, nine hundred twenty-one".