15664997 has 4 divisors (see below), whose sum is σ = 15879660. Its totient is φ = 15450336.

The previous prime is 15664967. The next prime is 15665009. The reversal of 15664997 is 79946651.

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

It can be written as a sum of positive squares in 2 ways, for example, as 5924356 + 9740641 = 2434^2 + 3121^2 .

It is a cyclic number.

It is not a de Polignac number, because 15664997 - 2⁶ = 15664933 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 (15664927) 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, 107222 + ... + 107367.

It is an arithmetic number, because the mean of its divisors is an integer number (3969915).

Almost surely, 2^15664997 is an apocalyptic number.

It is an amenable number.

15664997 is a deficient number, since it is larger than the sum of its proper divisors (214663).

15664997 is an equidigital number, since it uses as much as digits as its factorization.

15664997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214662.

The product of its digits is 408240, while the sum is 47.

The square root of 15664997 is about 3957.9031064441. The cubic root of 15664997 is about 250.2131355746.

It can be divided in two parts, 15664 and 997, that added together give a palindrome (16661).

The spelling of 15664997 in words is "fifteen million, six hundred sixty-four thousand, nine hundred ninety-seven".