8390990921 has 2 divisors, whose sum is σ = 8390990922. Its totient is φ = 8390990920.

The previous prime is 8390990903. The next prime is 8390990953. The reversal of 8390990921 is 1290990938.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 8170171321 + 220819600 = 90389^2 + 14860^2 .

It is a cyclic number.

It is not a de Polignac number, because 8390990921 - 2⁶ = 8390990857 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 8390990921.

It is not a weakly prime, because it can be changed into another prime (8390990821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4195495460 + 4195495461.

It is an arithmetic number, because the mean of its divisors is an integer number (4195495461).

Almost surely, 2^8390990921 is an apocalyptic number.

It is an amenable number.

8390990921 is a deficient number, since it is larger than the sum of its proper divisors (1).

8390990921 is an equidigital number, since it uses as much as digits as its factorization.

8390990921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 314928, while the sum is 50.

The square root of 8390990921 is about 91602.3521586646. The cubic root of 8390990921 is about 2032.0657238989.

The spelling of 8390990921 in words is "eight billion, three hundred ninety million, nine hundred ninety thousand, nine hundred twenty-one".