990424021 has 2 divisors, whose sum is σ = 990424022. Its totient is φ = 990424020.

The previous prime is 990424013. The next prime is 990424033. The reversal of 990424021 is 120424099.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 888636100 + 101787921 = 29810^2 + 10089^2 .

It is an emirp because it is prime and its reverse (120424099) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 990424021 - 2³ = 990424013 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (990424081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495212010 + 495212011.

It is an arithmetic number, because the mean of its divisors is an integer number (495212011).

Almost surely, 2^990424021 is an apocalyptic number.

It is an amenable number.

990424021 is a deficient number, since it is larger than the sum of its proper divisors (1).

990424021 is an equidigital number, since it uses as much as digits as its factorization.

990424021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5184, while the sum is 31.

The square root of 990424021 is about 31471.0028597755. The cubic root of 990424021 is about 996.7977636278.

The spelling of 990424021 in words is "nine hundred ninety million, four hundred twenty-four thousand, twenty-one".