21621268799 has 4 divisors (see below), whose sum is σ = 23284443336. Its totient is φ = 19958094264.

The previous prime is 21621268789. The next prime is 21621268807. The reversal of 21621268799 is 99786212612.

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 21621268799 - 2⁴ = 21621268783 is a prime.

It is a super-2 number, since 2×21621268799² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21621268799.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21621268759) 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, 831587249 + ... + 831587274.

It is an arithmetic number, because the mean of its divisors is an integer number (5821110834).

Almost surely, 2^21621268799 is an apocalyptic number.

21621268799 is a deficient number, since it is larger than the sum of its proper divisors (1663174537).

21621268799 is a wasteful number, since it uses less digits than its factorization.

21621268799 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1663174536.

The product of its digits is 1306368, while the sum is 53.

The spelling of 21621268799 in words is "twenty-one billion, six hundred twenty-one million, two hundred sixty-eight thousand, seven hundred ninety-nine".