15121921 has 4 divisors (see below), whose sum is σ = 15443712. Its totient is φ = 14800132.

The previous prime is 15121903. The next prime is 15121973. The reversal of 15121921 is 12912151.

15121921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 15121921 - 2⁵ = 15121889 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 15121892 and 15121901.

It is not an unprimeable number, because it can be changed into a prime (15121991) 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, 160825 + ... + 160918.

It is an arithmetic number, because the mean of its divisors is an integer number (3860928).

Almost surely, 2^15121921 is an apocalyptic number.

It is an amenable number.

15121921 is a deficient number, since it is larger than the sum of its proper divisors (321791).

15121921 is an equidigital number, since it uses as much as digits as its factorization.

15121921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 321790.

The product of its digits is 180, while the sum is 22.

The square root of 15121921 is about 3888.6914251455. The cubic root of 15121921 is about 247.2875897528.

The spelling of 15121921 in words is "fifteen million, one hundred twenty-one thousand, nine hundred twenty-one".