21121021999 has 16 divisors (see below), whose sum is σ = 26336192256. Its totient is φ = 16455758400.

The previous prime is 21121021991. The next prime is 21121022017. The reversal of 21121021999 is 99912012112.

It is a cyclic number.

It is not a de Polignac number, because 21121021999 - 2³ = 21121021991 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121021991) 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 15 ways as a sum of consecutive naturals, for example, 810379 + ... + 836035.

It is an arithmetic number, because the mean of its divisors is an integer number (1646012016).

Almost surely, 2^21121021999 is an apocalyptic number.

21121021999 is a deficient number, since it is larger than the sum of its proper divisors (5215170257).

21121021999 is a wasteful number, since it uses less digits than its factorization.

21121021999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36366.

The product of its (nonzero) digits is 5832, while the sum is 37.

The spelling of 21121021999 in words is "twenty-one billion, one hundred twenty-one million, twenty-one thousand, nine hundred ninety-nine".