21100021999 has 4 divisors (see below), whose sum is σ = 24114310864. Its totient is φ = 18085733136.

The previous prime is 21100021993. The next prime is 21100022023. The reversal of 21100021999 is 99912000112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21100021999 - 2²⁹ = 20563151087 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21100021993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1507144422 + ... + 1507144435.

It is an arithmetic number, because the mean of its divisors is an integer number (6028577716).

Almost surely, 2^21100021999 is an apocalyptic number.

21100021999 is a deficient number, since it is larger than the sum of its proper divisors (3014288865).

21100021999 is an equidigital number, since it uses as much as digits as its factorization.

21100021999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3014288864.

The product of its (nonzero) digits is 2916, while the sum is 34.

The spelling of 21100021999 in words is "twenty-one billion, one hundred million, twenty-one thousand, nine hundred ninety-nine".