15640661 has 4 divisors (see below), whose sum is σ = 15861024. Its totient is φ = 15420300.

The previous prime is 15640649. The next prime is 15640687. The reversal of 15640661 is 16604651.

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 a de Polignac number, because none of the positive numbers 2^k-15640661 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a nialpdrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15640861) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 110075 + ... + 110216.

It is an arithmetic number, because the mean of its divisors is an integer number (3965256).

Almost surely, 2^15640661 is an apocalyptic number.

It is an amenable number.

15640661 is a deficient number, since it is larger than the sum of its proper divisors (220363).

15640661 is an equidigital number, since it uses as much as digits as its factorization.

15640661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 220362.

The product of its (nonzero) digits is 4320, while the sum is 29.

The square root of 15640661 is about 3954.8275562912. The cubic root of 15640661 is about 250.0834974429.

The spelling of 15640661 in words is "fifteen million, six hundred forty thousand, six hundred sixty-one".