21609728783999 has 4 divisors (see below), whose sum is σ = 21752839570800. Its totient is φ = 21466617997200.

The previous prime is 21609728783971. The next prime is 21609728784031. The reversal of 21609728783999 is 99938782790612.

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-21609728783999 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 (21609728783939) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 71555393174 + ... + 71555393475.

It is an arithmetic number, because the mean of its divisors is an integer number (5438209892700).

Almost surely, 2^{21609728783999} is an apocalyptic number.

21609728783999 is a deficient number, since it is larger than the sum of its proper divisors (143110786801).

21609728783999 is a wasteful number, since it uses less digits than its factorization.

21609728783999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 143110786800.

The product of its (nonzero) digits is 1481421312, while the sum is 80.

The spelling of 21609728783999 in words is "twenty-one trillion, six hundred nine billion, seven hundred twenty-eight million, seven hundred eighty-three thousand, nine hundred ninety-nine".