15664861 has 4 divisors (see below), whose sum is σ = 15921724. Its totient is φ = 15408000.

The previous prime is 15664841. The next prime is 15664867. The reversal of 15664861 is 16846651.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16846651 = 29 ⋅580919.

It can be written as a sum of positive squares in 2 ways, for example, as 1368900 + 14295961 = 1170^2 + 3781^2 .

It is a cyclic number.

It is not a de Polignac number, because 15664861 - 2¹⁷ = 15533789 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 15664861.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15664867) 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, 128340 + ... + 128461.

It is an arithmetic number, because the mean of its divisors is an integer number (3980431).

Almost surely, 2^15664861 is an apocalyptic number.

It is an amenable number.

15664861 is a deficient number, since it is larger than the sum of its proper divisors (256863).

15664861 is an equidigital number, since it uses as much as digits as its factorization.

15664861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 256862.

The product of its digits is 34560, while the sum is 37.

The square root of 15664861 is about 3957.8859255921. The cubic root of 15664861 is about 250.2124114743.

The spelling of 15664861 in words is "fifteen million, six hundred sixty-four thousand, eight hundred sixty-one".