15661281 has 4 divisors (see below), whose sum is σ = 20881712. Its totient is φ = 10440852.

The previous prime is 15661279. The next prime is 15661291. The reversal of 15661281 is 18216651.

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 not a de Polignac number, because 15661281 - 2¹ = 15661279 is a prime.

It is a super-2 number, since 2×15661281² = 490551445121922, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (15661291) 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, 2610211 + ... + 2610216.

It is an arithmetic number, because the mean of its divisors is an integer number (5220428).

Almost surely, 2^15661281 is an apocalyptic number.

It is an amenable number.

15661281 is a deficient number, since it is larger than the sum of its proper divisors (5220431).

15661281 is an equidigital number, since it uses as much as digits as its factorization.

15661281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5220430.

The product of its digits is 2880, while the sum is 30.

The square root of 15661281 is about 3957.4336381044. The cubic root of 15661281 is about 250.1933490926.

The spelling of 15661281 in words is "fifteen million, six hundred sixty-one thousand, two hundred eighty-one".