31230821 has 2 divisors, whose sum is σ = 31230822. Its totient is φ = 31230820.

The previous prime is 31230817. The next prime is 31230929. The reversal of 31230821 is 12803213.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 29757025 + 1473796 = 5455^2 + 1214^2 .

It is an emirp because it is prime and its reverse (12803213) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 31230821 - 2² = 31230817 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 31230793 and 31230802.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31230811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15615410 + 15615411.

It is an arithmetic number, because the mean of its divisors is an integer number (15615411).

Almost surely, 2^31230821 is an apocalyptic number.

It is an amenable number.

31230821 is a deficient number, since it is larger than the sum of its proper divisors (1).

31230821 is an equidigital number, since it uses as much as digits as its factorization.

31230821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 288, while the sum is 20.

The square root of 31230821 is about 5588.4542585584. The cubic root of 31230821 is about 314.9158118847.

The spelling of 31230821 in words is "thirty-one million, two hundred thirty thousand, eight hundred twenty-one".