390999221 has 2 divisors, whose sum is σ = 390999222. Its totient is φ = 390999220.

The previous prime is 390999197. The next prime is 390999263. The reversal of 390999221 is 122999093.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 365344996 + 25654225 = 19114^2 + 5065^2 .

It is a cyclic number.

It is not a de Polignac number, because 390999221 - 2¹⁸ = 390737077 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (390999121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 195499610 + 195499611.

It is an arithmetic number, because the mean of its divisors is an integer number (195499611).

Almost surely, 2^390999221 is an apocalyptic number.

It is an amenable number.

390999221 is a deficient number, since it is larger than the sum of its proper divisors (1).

390999221 is an equidigital number, since it uses as much as digits as its factorization.

390999221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 78732, while the sum is 44.

The square root of 390999221 is about 19773.7002354137. The cubic root of 390999221 is about 731.2377955350.

The spelling of 390999221 in words is "three hundred ninety million, nine hundred ninety-nine thousand, two hundred twenty-one".