21918919 has 16 divisors (see below), whose sum is σ = 24504480. Its totient is φ = 19440000.

The previous prime is 21918881. The next prime is 21919003. The reversal of 21918919 is 91981912.

It is a cyclic number.

It is not a de Polignac number, because 21918919 - 2⁷ = 21918791 is a prime.

It is a super-2 number, since 2×21918919² = 960878020257122, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21918019) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 121009 + ... + 121189.

It is an arithmetic number, because the mean of its divisors is an integer number (1531530).

Almost surely, 2^21918919 is an apocalyptic number.

21918919 is a deficient number, since it is larger than the sum of its proper divisors (2585561).

21918919 is a wasteful number, since it uses less digits than its factorization.

21918919 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 402.

The product of its digits is 11664, while the sum is 40.

The square root of 21918919 is about 4681.7645177860. The cubic root of 21918919 is about 279.8592787786.

The spelling of 21918919 in words is "twenty-one million, nine hundred eighteen thousand, nine hundred nineteen".