31491409 has 4 divisors (see below), whose sum is σ = 31574016. Its totient is φ = 31408804.

The previous prime is 31491401. The next prime is 31491461. The reversal of 31491409 is 90419413.

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 a cyclic number.

It is not a de Polignac number, because 31491409 - 2³ = 31491401 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31491401) 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, 40729 + ... + 41494.

It is an arithmetic number, because the mean of its divisors is an integer number (7893504).

Almost surely, 2^31491409 is an apocalyptic number.

It is an amenable number.

31491409 is a deficient number, since it is larger than the sum of its proper divisors (82607).

31491409 is an equidigital number, since it uses as much as digits as its factorization.

31491409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82606.

The product of its (nonzero) digits is 3888, while the sum is 31.

The square root of 31491409 is about 5611.7206808607. The cubic root of 31491409 is about 315.7892662430.

The spelling of 31491409 in words is "thirty-one million, four hundred ninety-one thousand, four hundred nine".