21551858999 has 4 divisors (see below), whose sum is σ = 23511118920. Its totient is φ = 19592599080.

The previous prime is 21551858983. The next prime is 21551859019. The reversal of 21551858999 is 99985815512.

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 21551858999 - 2⁴ = 21551858983 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 (21551858969) 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, 979629944 + ... + 979629965.

It is an arithmetic number, because the mean of its divisors is an integer number (5877779730).

Almost surely, 2^21551858999 is an apocalyptic number.

21551858999 is a deficient number, since it is larger than the sum of its proper divisors (1959259921).

21551858999 is a wasteful number, since it uses less digits than its factorization.

21551858999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1959259920.

The product of its digits is 11664000, while the sum is 62.

The spelling of 21551858999 in words is "twenty-one billion, five hundred fifty-one million, eight hundred fifty-eight thousand, nine hundred ninety-nine".