12991531 has 4 divisors (see below), whose sum is σ = 14847472. Its totient is φ = 11135592.

The previous prime is 12991523. The next prime is 12991541. The reversal of 12991531 is 13519921.

It is a happy number.

12991531 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 13519921 = 709 ⋅19069.

It is a cyclic number.

It is not a de Polignac number, because 12991531 - 2³ = 12991523 is a prime.

It is a super-2 number, since 2×12991531² = 337559755447922, 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 = 12991493 and 12991502.

It is not an unprimeable number, because it can be changed into a prime (12991541) 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, 927960 + ... + 927973.

It is an arithmetic number, because the mean of its divisors is an integer number (3711868).

Almost surely, 2^12991531 is an apocalyptic number.

12991531 is a deficient number, since it is larger than the sum of its proper divisors (1855941).

12991531 is an equidigital number, since it uses as much as digits as its factorization.

12991531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1855940.

The product of its digits is 2430, while the sum is 31.

The square root of 12991531 is about 3604.3766451357. The cubic root of 12991531 is about 235.0823975431.

The spelling of 12991531 in words is "twelve million, nine hundred ninety-one thousand, five hundred thirty-one".