15717921 has 16 divisors (see below), whose sum is σ = 22155840. Its totient is φ = 9884160.

The previous prime is 15717907. The next prime is 15717941. The reversal of 15717921 is 12971751.

It is not a de Polignac number, because 15717921 - 2¹¹ = 15715873 is a prime.

It is not an unprimeable number, because it can be changed into a prime (15717941) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17401 + ... + 18281.

It is an arithmetic number, because the mean of its divisors is an integer number (1384740).

Almost surely, 2^15717921 is an apocalyptic number.

It is an amenable number.

15717921 is a deficient number, since it is larger than the sum of its proper divisors (6437919).

15717921 is a wasteful number, since it uses less digits than its factorization.

15717921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1216.

The product of its digits is 4410, while the sum is 33.

The square root of 15717921 is about 3964.5833324575. The cubic root of 15717921 is about 250.4945995067.

The spelling of 15717921 in words is "fifteen million, seven hundred seventeen thousand, nine hundred twenty-one".