31645021 has 2 divisors, whose sum is σ = 31645022. Its totient is φ = 31645020.

The previous prime is 31644979. The next prime is 31645037. The reversal of 31645021 is 12054613.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 29822521 + 1822500 = 5461^2 + 1350^2 .

It is an emirp because it is prime and its reverse (12054613) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31645021 is a prime.

It is a Chen prime.

It is a nialpdrome in base 12.

It is a junction number, because it is equal to n+sod(n) for n = 31644983 and 31645001.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31645091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15822510 + 15822511.

It is an arithmetic number, because the mean of its divisors is an integer number (15822511).

Almost surely, 2^31645021 is an apocalyptic number.

It is an amenable number.

31645021 is a deficient number, since it is larger than the sum of its proper divisors (1).

31645021 is an equidigital number, since it uses as much as digits as its factorization.

31645021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 31645021 is about 5625.3907419841. The cubic root of 31645021 is about 316.3018966321.

Adding to 31645021 its reverse (12054613), we get a palindrome (43699634).

The spelling of 31645021 in words is "thirty-one million, six hundred forty-five thousand, twenty-one".