31243021 has 4 divisors (see below), whose sum is σ = 31565212. Its totient is φ = 30920832.

The previous prime is 31243013. The next prime is 31243061. The reversal of 31243021 is 12034213.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12034213 = 37 ⋅325249.

It can be written as a sum of positive squares in 2 ways, for example, as 9954025 + 21288996 = 3155^2 + 4614^2 .

It is a cyclic number.

It is not a de Polignac number, because 31243021 - 2³ = 31243013 is a prime.

It is a super-2 number, since 2×31243021² = 1952252722412882, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 31242986 and 31243004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31243001) 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, 160950 + ... + 161143.

It is an arithmetic number, because the mean of its divisors is an integer number (7891303).

Almost surely, 2^31243021 is an apocalyptic number.

It is an amenable number.

31243021 is a deficient number, since it is larger than the sum of its proper divisors (322191).

31243021 is an equidigital number, since it uses as much as digits as its factorization.

31243021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322190.

The product of its (nonzero) digits is 144, while the sum is 16.

The square root of 31243021 is about 5589.5456881575. The cubic root of 31243021 is about 314.9568127573.

Adding to 31243021 its reverse (12034213), we get a palindrome (43277234).

The spelling of 31243021 in words is "thirty-one million, two hundred forty-three thousand, twenty-one".