531731021 has 2 divisors, whose sum is σ = 531731022. Its totient is φ = 531731020.

The previous prime is 531730967. The next prime is 531731023. The reversal of 531731021 is 120137135.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 517062121 + 14668900 = 22739^2 + 3830^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-531731021 is a prime.

Together with 531731023, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (531731023) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 265865510 + 265865511.

It is an arithmetic number, because the mean of its divisors is an integer number (265865511).

Almost surely, 2^531731021 is an apocalyptic number.

It is an amenable number.

531731021 is a deficient number, since it is larger than the sum of its proper divisors (1).

531731021 is an equidigital number, since it uses as much as digits as its factorization.

531731021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 630, while the sum is 23.

The square root of 531731021 is about 23059.2935928228. The cubic root of 531731021 is about 810.1473191377.

Adding to 531731021 its reverse (120137135), we get a palindrome (651868156).

The spelling of 531731021 in words is "five hundred thirty-one million, seven hundred thirty-one thousand, twenty-one".