21918516 has 12 divisors (see below), whose sum is σ = 51143232. Its totient is φ = 7306168.

The previous prime is 21918511. The next prime is 21918529. The reversal of 21918516 is 61581912.

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21918511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 913260 + ... + 913283.

It is an arithmetic number, because the mean of its divisors is an integer number (4261936).

Almost surely, 2^21918516 is an apocalyptic number.

It is an amenable number.

21918516 is an abundant number, since it is smaller than the sum of its proper divisors (29224716).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21918516 is a wasteful number, since it uses less digits than its factorization.

21918516 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1826550 (or 1826548 counting only the distinct ones).

The product of its digits is 4320, while the sum is 33.

The square root of 21918516 is about 4681.7214782599. The cubic root of 21918516 is about 279.8575636091.

The spelling of 21918516 in words is "twenty-one million, nine hundred eighteen thousand, five hundred sixteen".