15564991 has 4 divisors (see below), whose sum is σ = 16762312. Its totient is φ = 14367672.

The previous prime is 15564977. The next prime is 15565001. The reversal of 15564991 is 19946551.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19946551 = 313 ⋅63727.

It is a cyclic number.

It is not a de Polignac number, because 15564991 - 2⁷ = 15564863 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 (15564931) 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, 598641 + ... + 598666.

It is an arithmetic number, because the mean of its divisors is an integer number (4190578).

Almost surely, 2^15564991 is an apocalyptic number.

15564991 is a deficient number, since it is larger than the sum of its proper divisors (1197321).

15564991 is a wasteful number, since it uses less digits than its factorization.

15564991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1197320.

The product of its digits is 48600, while the sum is 40.

The square root of 15564991 is about 3945.2491683036. The cubic root of 15564991 is about 249.6795414007.

The spelling of 15564991 in words is "fifteen million, five hundred sixty-four thousand, nine hundred ninety-one".