15616921 has 4 divisors (see below), whose sum is σ = 15633792. Its totient is φ = 15600052.

The previous prime is 15616907. The next prime is 15616933. The reversal of 15616921 is 12961651.

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, and also an emirpimes, since its reverse is a distinct semiprime: 12961651 = 59 ⋅219689.

It is a cyclic number.

It is not a de Polignac number, because 15616921 - 2⁵ = 15616889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15616961) 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, 6961 + ... + 8926.

It is an arithmetic number, because the mean of its divisors is an integer number (3908448).

Almost surely, 2^15616921 is an apocalyptic number.

It is an amenable number.

15616921 is a deficient number, since it is larger than the sum of its proper divisors (16871).

15616921 is an equidigital number, since it uses as much as digits as its factorization.

15616921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16870.

The product of its digits is 3240, while the sum is 31.

The square root of 15616921 is about 3951.8250214300. The cubic root of 15616921 is about 249.9569045716.

The spelling of 15616921 in words is "fifteen million, six hundred sixteen thousand, nine hundred twenty-one".