999621209 has 2 divisors, whose sum is σ = 999621210. Its totient is φ = 999621208.

The previous prime is 999621163. The next prime is 999621241. The reversal of 999621209 is 902126999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 965655625 + 33965584 = 31075^2 + 5828^2 .

It is a cyclic number.

It is not a de Polignac number, because 999621209 - 2²⁸ = 731185753 is a prime.

It is a super-2 number, since 2×999621209² = 1998485122965243362, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (999621269) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499810604 + 499810605.

It is an arithmetic number, because the mean of its divisors is an integer number (499810605).

Almost surely, 2^999621209 is an apocalyptic number.

It is an amenable number.

999621209 is a deficient number, since it is larger than the sum of its proper divisors (1).

999621209 is an equidigital number, since it uses as much as digits as its factorization.

999621209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 157464, while the sum is 47.

The square root of 999621209 is about 31616.7868228256. The cubic root of 999621209 is about 999.8737203875.

The spelling of 999621209 in words is "nine hundred ninety-nine million, six hundred twenty-one thousand, two hundred nine".