15691921 has 8 divisors (see below), whose sum is σ = 18512384. Its totient is φ = 13016160.

The previous prime is 15691903. The next prime is 15691931. The reversal of 15691921 is 12919651.

It is a happy number.

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 15691921 - 2⁹ = 15691409 is a prime.

It is a Duffinian number.

It is a plaindrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (15691931) 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 7 ways as a sum of consecutive naturals, for example, 35940 + ... + 36373.

It is an arithmetic number, because the mean of its divisors is an integer number (2314048).

Almost surely, 2^15691921 is an apocalyptic number.

It is an amenable number.

15691921 is a deficient number, since it is larger than the sum of its proper divisors (2820463).

15691921 is an equidigital number, since it uses as much as digits as its factorization.

15691921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72351.

The product of its digits is 4860, while the sum is 34.

The square root of 15691921 is about 3961.3029422148. The cubic root of 15691921 is about 250.3564036643.

The spelling of 15691921 in words is "fifteen million, six hundred ninety-one thousand, nine hundred twenty-one".