21981899 has 8 divisors (see below), whose sum is σ = 22482192. Its totient is φ = 21486240.

The previous prime is 21981893. The next prime is 21981923. The reversal of 21981899 is 99818912.

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 21981899 - 2²⁰ = 20933323 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21981893) 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, 9512 + ... + 11594.

It is an arithmetic number, because the mean of its divisors is an integer number (2810274).

Almost surely, 2^21981899 is an apocalyptic number.

21981899 is a deficient number, since it is larger than the sum of its proper divisors (500293).

21981899 is a wasteful number, since it uses less digits than its factorization.

21981899 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2317.

The product of its digits is 93312, while the sum is 47.

The square root of 21981899 is about 4688.4857896767. The cubic root of 21981899 is about 280.1270639283.

The spelling of 21981899 in words is "twenty-one million, nine hundred eighty-one thousand, eight hundred ninety-nine".