15721391 has 8 divisors (see below), whose sum is σ = 18069120. Its totient is φ = 13399128.

The previous prime is 15721373. The next prime is 15721421. The reversal of 15721391 is 19312751.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 15721391 - 2¹⁴ = 15705007 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15721301) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5021 + ... + 7526.

It is an arithmetic number, because the mean of its divisors is an integer number (2258640).

Almost surely, 2^15721391 is an apocalyptic number.

15721391 is a deficient number, since it is larger than the sum of its proper divisors (2347729).

15721391 is a wasteful number, since it uses less digits than its factorization.

15721391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12733.

The product of its digits is 1890, while the sum is 29.

The square root of 15721391 is about 3965.0209331099. The cubic root of 15721391 is about 250.5130318066.

The spelling of 15721391 in words is "fifteen million, seven hundred twenty-one thousand, three hundred ninety-one".