15639661 has 4 divisors (see below), whose sum is σ = 15904800. Its totient is φ = 15374524.

The previous prime is 15639599. The next prime is 15639691. The reversal of 15639661 is 16693651.

It is the 1615-th star number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 15639661 - 2²³ = 7251053 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 15639661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15639691) 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, 132481 + ... + 132598.

It is an arithmetic number, because the mean of its divisors is an integer number (3976200).

Almost surely, 2^15639661 is an apocalyptic number.

It is an amenable number.

15639661 is a deficient number, since it is larger than the sum of its proper divisors (265139).

15639661 is an equidigital number, since it uses as much as digits as its factorization.

15639661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 265138.

The product of its digits is 29160, while the sum is 37.

The square root of 15639661 is about 3954.7011265075. The cubic root of 15639661 is about 250.0781675568.

The spelling of 15639661 in words is "fifteen million, six hundred thirty-nine thousand, six hundred sixty-one".