15916221 has 24 divisors (see below), whose sum is σ = 23721984. Its totient is φ = 10278240.

The previous prime is 15916217. The next prime is 15916223. The reversal of 15916221 is 12261951.

It is not a de Polignac number, because 15916221 - 2² = 15916217 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15916223) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 80695 + ... + 80891.

It is an arithmetic number, because the mean of its divisors is an integer number (988416).

Almost surely, 2^15916221 is an apocalyptic number.

It is an amenable number.

15916221 is a deficient number, since it is larger than the sum of its proper divisors (7805763).

15916221 is a wasteful number, since it uses less digits than its factorization.

15916221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 441 (or 438 counting only the distinct ones).

The product of its digits is 1080, while the sum is 27.

The square root of 15916221 is about 3989.5138801613. The cubic root of 15916221 is about 251.5436279015.

The spelling of 15916221 in words is "fifteen million, nine hundred sixteen thousand, two hundred twenty-one".