15661642 has 4 divisors (see below), whose sum is σ = 23492466. Its totient is φ = 7830820.

The previous prime is 15661637. The next prime is 15661651. The reversal of 15661642 is 24616651.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 24616651 = 2011 ⋅12241.

It can be written as a sum of positive squares in only one way, i.e., 12047841 + 3613801 = 3471^2 + 1901^2 .

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3915409 + ... + 3915412.

Almost surely, 2^15661642 is an apocalyptic number.

15661642 is a deficient number, since it is larger than the sum of its proper divisors (7830824).

15661642 is an equidigital number, since it uses as much as digits as its factorization.

15661642 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7830823.

The product of its digits is 8640, while the sum is 31.

The square root of 15661642 is about 3957.4792482084. The cubic root of 15661642 is about 250.1952714366.

The spelling of 15661642 in words is "fifteen million, six hundred sixty-one thousand, six hundred forty-two".