21918357 has 12 divisors (see below), whose sum is σ = 32832800. Its totient is φ = 14612076.

The previous prime is 21918353. The next prime is 21918359. The reversal of 21918357 is 75381912.

It is not a de Polignac number, because 21918357 - 2² = 21918353 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 (21918353) 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 11 ways as a sum of consecutive naturals, for example, 44857 + ... + 45342.

Almost surely, 2^21918357 is an apocalyptic number.

21918357 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21918357 is a deficient number, since it is larger than the sum of its proper divisors (10914443).

21918357 is an frugal number, since it uses more digits than its factorization.

21918357 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90214 (or 90202 counting only the distinct ones).

The product of its digits is 15120, while the sum is 36.

The square root of 21918357 is about 4681.7044972958. The cubic root of 21918357 is about 279.8568868988.

The spelling of 21918357 in words is "twenty-one million, nine hundred eighteen thousand, three hundred fifty-seven".