31321681 has 4 divisors (see below), whose sum is σ = 31673700. Its totient is φ = 30969664.

The previous prime is 31321651. The next prime is 31321691. The reversal of 31321681 is 18612313.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18612313 = 23 ⋅809231.

It can be written as a sum of positive squares in 2 ways, for example, as 7750656 + 23571025 = 2784^2 + 4855^2 .

It is a cyclic number.

It is not a de Polignac number, because 31321681 - 2⁵ = 31321649 is a prime.

It is a super-2 number, since 2×31321681² = 1962095401331522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31321651) 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, 175876 + ... + 176053.

It is an arithmetic number, because the mean of its divisors is an integer number (7918425).

Almost surely, 2^31321681 is an apocalyptic number.

It is an amenable number.

31321681 is a deficient number, since it is larger than the sum of its proper divisors (352019).

31321681 is an equidigital number, since it uses as much as digits as its factorization.

31321681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 352018.

The product of its digits is 864, while the sum is 25.

The square root of 31321681 is about 5596.5776149358. The cubic root of 31321681 is about 315.2209116364.

Adding to 31321681 its reverse (18612313), we get a palindrome (49933994).

The spelling of 31321681 in words is "thirty-one million, three hundred twenty-one thousand, six hundred eighty-one".