21001011999 has 32 divisors (see below), whose sum is σ = 34046127360. Its totient is φ = 11348697600.

The previous prime is 21001011947. The next prime is 21001012007. The reversal of 21001011999 is 99911010012.

It is not a de Polignac number, because 21001011999 - 2⁹ = 21001011487 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001051999) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 974472 + ... + 995789.

It is an arithmetic number, because the mean of its divisors is an integer number (1063941480).

Almost surely, 2^21001011999 is an apocalyptic number.

21001011999 is a deficient number, since it is larger than the sum of its proper divisors (13045115361).

21001011999 is a wasteful number, since it uses less digits than its factorization.

21001011999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1970311.

The product of its (nonzero) digits is 1458, while the sum is 33.

The spelling of 21001011999 in words is "twenty-one billion, one million, eleven thousand, nine hundred ninety-nine".