31531421 has 2 divisors, whose sum is σ = 31531422. Its totient is φ = 31531420.

The previous prime is 31531417. The next prime is 31531453. The reversal of 31531421 is 12413513.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 25351225 + 6180196 = 5035^2 + 2486^2 .

It is a cyclic number.

It is not a de Polignac number, because 31531421 - 2² = 31531417 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 31531393 and 31531402.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31531471) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15765710 + 15765711.

It is an arithmetic number, because the mean of its divisors is an integer number (15765711).

Almost surely, 2^31531421 is an apocalyptic number.

It is an amenable number.

31531421 is a deficient number, since it is larger than the sum of its proper divisors (1).

31531421 is an equidigital number, since it uses as much as digits as its factorization.

31531421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 360, while the sum is 20.

The square root of 31531421 is about 5615.2845876233. The cubic root of 31531421 is about 315.9229536299.

Adding to 31531421 its reverse (12413513), we get a palindrome (43944934).

The spelling of 31531421 in words is "thirty-one million, five hundred thirty-one thousand, four hundred twenty-one".