999872636621 has 2 divisors, whose sum is σ = 999872636622. Its totient is φ = 999872636620.

The previous prime is 999872636603. The next prime is 999872636627. The reversal of 999872636621 is 126636278999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 746390595721 + 253482040900 = 863939^2 + 503470^2 .

It is an emirp because it is prime and its reverse (126636278999) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 999872636621 - 2²² = 999868442317 is a prime.

It is a Sophie Germain 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 (999872636627) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499936318310 + 499936318311.

It is an arithmetic number, because the mean of its divisors is an integer number (499936318311).

Almost surely, 2^999872636621 is an apocalyptic number.

It is an amenable number.

999872636621 is a deficient number, since it is larger than the sum of its proper divisors (1).

999872636621 is an equidigital number, since it uses as much as digits as its factorization.

999872636621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 105815808, while the sum is 68.

The spelling of 999872636621 in words is "nine hundred ninety-nine billion, eight hundred seventy-two million, six hundred thirty-six thousand, six hundred twenty-one".