31621861 has 4 divisors (see below), whose sum is σ = 32712300. Its totient is φ = 30531424.

The previous prime is 31621847. The next prime is 31621879. The reversal of 31621861 is 16812613.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16812613 = 43 ⋅390991.

It can be written as a sum of positive squares in 2 ways, for example, as 14861025 + 16760836 = 3855^2 + 4094^2 .

It is a cyclic number.

It is not a de Polignac number, because 31621861 - 2¹³ = 31613669 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 (31621831) 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, 545176 + ... + 545233.

It is an arithmetic number, because the mean of its divisors is an integer number (8178075).

Almost surely, 2^31621861 is an apocalyptic number.

It is an amenable number.

31621861 is a deficient number, since it is larger than the sum of its proper divisors (1090439).

31621861 is a wasteful number, since it uses less digits than its factorization.

31621861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1090438.

The product of its digits is 1728, while the sum is 28.

The square root of 31621861 is about 5623.3318415331. The cubic root of 31621861 is about 316.2247139818.

The spelling of 31621861 in words is "thirty-one million, six hundred twenty-one thousand, eight hundred sixty-one".