31389221 has 2 divisors, whose sum is σ = 31389222. Its totient is φ = 31389220.

The previous prime is 31389187. The next prime is 31389233. The reversal of 31389221 is 12298313.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 28238596 + 3150625 = 5314^2 + 1775^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31389221 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31389251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15694610 + 15694611.

It is an arithmetic number, because the mean of its divisors is an integer number (15694611).

Almost surely, 2^31389221 is an apocalyptic number.

It is an amenable number.

31389221 is a deficient number, since it is larger than the sum of its proper divisors (1).

31389221 is an equidigital number, since it uses as much as digits as its factorization.

31389221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2592, while the sum is 29.

The square root of 31389221 is about 5602.6084103746. The cubic root of 31389221 is about 315.4473228124.

The spelling of 31389221 in words is "thirty-one million, three hundred eighty-nine thousand, two hundred twenty-one".