21951999991 has 8 divisors (see below), whose sum is σ = 22122234000. Its totient is φ = 21782071680.

The previous prime is 21951999983. The next prime is 21952000039. The reversal of 21951999991 is 19999915912.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21951999991 - 2³ = 21951999983 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 (21951999931) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 68815 + ... + 220543.

It is an arithmetic number, because the mean of its divisors is an integer number (2765279250).

Almost surely, 2^21951999991 is an apocalyptic number.

21951999991 is a deficient number, since it is larger than the sum of its proper divisors (170234009).

21951999991 is a wasteful number, since it uses less digits than its factorization.

21951999991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 152849.

The product of its digits is 5314410, while the sum is 64.

The spelling of 21951999991 in words is "twenty-one billion, nine hundred fifty-one million, nine hundred ninety-nine thousand, nine hundred ninety-one".