15663994 has 4 divisors (see below), whose sum is σ = 23495994. Its totient is φ = 7831996.

The previous prime is 15663979. The next prime is 15664003. The reversal of 15663994 is 49936651.

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

It can be written as a sum of positive squares in only one way, i.e., 15499969 + 164025 = 3937^2 + 405^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 15663994.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3915997 + ... + 3916000.

Almost surely, 2^15663994 is an apocalyptic number.

15663994 is a deficient number, since it is larger than the sum of its proper divisors (7832000).

15663994 is an equidigital number, since it uses as much as digits as its factorization.

15663994 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7831999.

The product of its digits is 174960, while the sum is 43.

The square root of 15663994 is about 3957.7763959072. The cubic root of 15663994 is about 250.2077952367.

The spelling of 15663994 in words is "fifteen million, six hundred sixty-three thousand, nine hundred ninety-four".