999506021 has 2 divisors, whose sum is σ = 999506022. Its totient is φ = 999506020.

The previous prime is 999505993. The next prime is 999506023. The reversal of 999506021 is 120605999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 583753921 + 415752100 = 24161^2 + 20390^2 .

It is an emirp because it is prime and its reverse (120605999) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 999506021 - 2²² = 995311717 is a prime.

Together with 999506023, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 999506021.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (999506023) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499753010 + 499753011.

It is an arithmetic number, because the mean of its divisors is an integer number (499753011).

Almost surely, 2^999506021 is an apocalyptic number.

It is an amenable number.

999506021 is a deficient number, since it is larger than the sum of its proper divisors (1).

999506021 is an equidigital number, since it uses as much as digits as its factorization.

999506021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 43740, while the sum is 41.

The square root of 999506021 is about 31614.9651431090. The cubic root of 999506021 is about 999.8353132131.

The spelling of 999506021 in words is "nine hundred ninety-nine million, five hundred six thousand, twenty-one".