15978791 has 4 divisors (see below), whose sum is σ = 16819800. Its totient is φ = 15137784.

The previous prime is 15978779. The next prime is 15978803. The reversal of 15978791 is 19787951.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (15978779) and next prime (15978803).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-15978791 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 (15978701) 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, 420476 + ... + 420513.

It is an arithmetic number, because the mean of its divisors is an integer number (4204950).

Almost surely, 2^15978791 is an apocalyptic number.

15978791 is a deficient number, since it is larger than the sum of its proper divisors (841009).

15978791 is an equidigital number, since it uses as much as digits as its factorization.

15978791 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 841008.

The product of its digits is 158760, while the sum is 47.

The square root of 15978791 is about 3997.3479958593. The cubic root of 15978791 is about 251.8728204734.

The spelling of 15978791 in words is "fifteen million, nine hundred seventy-eight thousand, seven hundred ninety-one".