21100999 has 2 divisors, whose sum is σ = 21101000. Its totient is φ = 21100998.

The previous prime is 21100993. The next prime is 21101027. The reversal of 21100999 is 99900112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21100999 - 2⁵ = 21100967 is a prime.

It is a super-3 number, since 3×21100999³ (a number of 23 digits) contains 333 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21100999.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21100993) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10550499 + 10550500.

It is an arithmetic number, because the mean of its divisors is an integer number (10550500).

Almost surely, 2^21100999 is an apocalyptic number.

21100999 is a deficient number, since it is larger than the sum of its proper divisors (1).

21100999 is an equidigital number, since it uses as much as digits as its factorization.

21100999 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1458, while the sum is 31.

The square root of 21100999 is about 4593.5823710912. The cubic root of 21100999 is about 276.3340097885.

The spelling of 21100999 in words is "twenty-one million, one hundred thousand, nine hundred ninety-nine".