31321021 has 4 divisors (see below), whose sum is σ = 33163452. Its totient is φ = 29478592.

The previous prime is 31321013. The next prime is 31321033. The reversal of 31321021 is 12012313.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12012313 = 19 ⋅632227.

It can be written as a sum of positive squares in 2 ways, for example, as 22992025 + 8328996 = 4795^2 + 2886^2 .

It is a cyclic number.

It is not a de Polignac number, because 31321021 - 2³ = 31321013 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 31320992 and 31321010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31321321) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 921190 + ... + 921223.

It is an arithmetic number, because the mean of its divisors is an integer number (8290863).

Almost surely, 2^31321021 is an apocalyptic number.

It is an amenable number.

31321021 is a deficient number, since it is larger than the sum of its proper divisors (1842431).

31321021 is a wasteful number, since it uses less digits than its factorization.

31321021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1842430.

The product of its (nonzero) digits is 36, while the sum is 13.

The square root of 31321021 is about 5596.5186500181. The cubic root of 31321021 is about 315.2186975443.

Adding to 31321021 its reverse (12012313), we get a palindrome (43333334).

The spelling of 31321021 in words is "thirty-one million, three hundred twenty-one thousand, twenty-one".