31355221 has 2 divisors, whose sum is σ = 31355222. Its totient is φ = 31355220.

The previous prime is 31355197. The next prime is 31355297. The reversal of 31355221 is 12255313.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 23902321 + 7452900 = 4889^2 + 2730^2 .

It is a cyclic number.

It is not a de Polignac number, because 31355221 - 2²¹ = 29258069 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 31355192 and 31355201.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31355321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15677610 + 15677611.

It is an arithmetic number, because the mean of its divisors is an integer number (15677611).

Almost surely, 2^31355221 is an apocalyptic number.

It is an amenable number.

31355221 is a deficient number, since it is larger than the sum of its proper divisors (1).

31355221 is an equidigital number, since it uses as much as digits as its factorization.

31355221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 900, while the sum is 22.

The square root of 31355221 is about 5599.5732873140. The cubic root of 31355221 is about 315.3333868455. Note that the first 4 decimals are identical.

The spelling of 31355221 in words is "thirty-one million, three hundred fifty-five thousand, two hundred twenty-one".