31881389 has 4 divisors (see below), whose sum is σ = 31893180. Its totient is φ = 31869600.

The previous prime is 31881371. The next prime is 31881401. The reversal of 31881389 is 98318813.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 98318813 = 23 ⋅4274731.

It can be written as a sum of positive squares in 2 ways, for example, as 990025 + 30891364 = 995^2 + 5558^2 .

It is a cyclic number.

It is not a de Polignac number, because 31881389 - 2¹⁶ = 31815853 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31881329) 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, 407 + ... + 7995.

It is an arithmetic number, because the mean of its divisors is an integer number (7973295).

Almost surely, 2^31881389 is an apocalyptic number.

It is an amenable number.

31881389 is a deficient number, since it is larger than the sum of its proper divisors (11791).

31881389 is an equidigital number, since it uses as much as digits as its factorization.

31881389 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11790.

The product of its digits is 41472, while the sum is 41.

The square root of 31881389 is about 5646.3606863182. The cubic root of 31881389 is about 317.0874680265.

The spelling of 31881389 in words is "thirty-one million, eight hundred eighty-one thousand, three hundred eighty-nine".