15661321 has 8 divisors (see below), whose sum is σ = 17599680. Its totient is φ = 13827792.

The previous prime is 15661309. The next prime is 15661333. The reversal of 15661321 is 12316651.

It is an interprime number because it is at equal distance from previous prime (15661309) and next prime (15661333).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 15661321 - 2⁷ = 15661193 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15661351) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 25891 + ... + 26488.

It is an arithmetic number, because the mean of its divisors is an integer number (2199960).

Almost surely, 2^15661321 is an apocalyptic number.

It is an amenable number.

15661321 is a deficient number, since it is larger than the sum of its proper divisors (1938359).

15661321 is a wasteful number, since it uses less digits than its factorization.

15661321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52415.

The product of its digits is 1080, while the sum is 25.

The square root of 15661321 is about 3957.4386918814. The cubic root of 15661321 is about 250.1935620962.

Adding to 15661321 its reverse (12316651), we get a palindrome (27977972).

The spelling of 15661321 in words is "fifteen million, six hundred sixty-one thousand, three hundred twenty-one".