15661231 has 4 divisors (see below), whose sum is σ = 16166464. Its totient is φ = 15156000.

The previous prime is 15661223. The next prime is 15661273. The reversal of 15661231 is 13216651.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 15661231 - 2³ = 15661223 is a prime.

It is a super-2 number, since 2×15661231² = 490548312870722, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 15661196 and 15661205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15661291) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 252570 + ... + 252631.

It is an arithmetic number, because the mean of its divisors is an integer number (4041616).

Almost surely, 2^15661231 is an apocalyptic number.

15661231 is a deficient number, since it is larger than the sum of its proper divisors (505233).

15661231 is an equidigital number, since it uses as much as digits as its factorization.

15661231 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 505232.

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

The square root of 15661231 is about 3957.4273208740. The cubic root of 15661231 is about 250.1930828377.

Adding to 15661231 its reverse (13216651), we get a palindrome (28877882).

The spelling of 15661231 in words is "fifteen million, six hundred sixty-one thousand, two hundred thirty-one".