21001211999 has 4 divisors (see below), whose sum is σ = 21397461336. Its totient is φ = 20604962664.

The previous prime is 21001211977. The next prime is 21001212007. The reversal of 21001211999 is 99911210012.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21001211999 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001211939) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 198124589 + ... + 198124694.

It is an arithmetic number, because the mean of its divisors is an integer number (5349365334).

Almost surely, 2^21001211999 is an apocalyptic number.

21001211999 is a deficient number, since it is larger than the sum of its proper divisors (396249337).

21001211999 is an equidigital number, since it uses as much as digits as its factorization.

21001211999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 396249336.

The product of its (nonzero) digits is 2916, while the sum is 35.

The spelling of 21001211999 in words is "twenty-one billion, one million, two hundred eleven thousand, nine hundred ninety-nine".