31820881 has 3 divisors (see below), whose sum is σ = 31826523. Its totient is φ = 31815240.

The previous prime is 31820869. The next prime is 31820897. The reversal of 31820881 is 18802813.

The square root of 31820881 is 5641.

It is a perfect power (a square), and thus also a powerful 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: 18802813 = 67 ⋅280639.

It can be written as a sum of positive squares in only one way, i.e., 31460881 + 360000 = 5609^2 + 600^2 .

It is not a de Polignac number, because 31820881 - 2¹¹ = 31818833 is a prime.

It is a super-2 number, since 2×31820881² = 2025136935232322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31820861) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 2821 + ... + 8461.

It is an arithmetic number, because the mean of its divisors is an integer number (10608841).

Almost surely, 2^31820881 is an apocalyptic number.

31820881 is the 5641-st square number.

31820881 is the 2821-st centered octagonal number.

It is an amenable number.

31820881 is a deficient number, since it is larger than the sum of its proper divisors (5642).

31820881 is an frugal number, since it uses more digits than its factorization.

31820881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11282 (or 5641 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 31.

The cubic root of 31820881 is about 316.8867398493.

The spelling of 31820881 in words is "thirty-one million, eight hundred twenty thousand, eight hundred eighty-one".