21718557 has 16 divisors (see below), whose sum is σ = 36772480. Its totient is φ = 12410496.

The previous prime is 21718553. The next prime is 21718583. The reversal of 21718557 is 75581712.

It is not a de Polignac number, because 21718557 - 2² = 21718553 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 (21718553) 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 15 ways as a sum of consecutive naturals, for example, 57268 + ... + 57645.

It is an arithmetic number, because the mean of its divisors is an integer number (2298280).

Almost surely, 2^21718557 is an apocalyptic number.

21718557 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21718557 is a deficient number, since it is larger than the sum of its proper divisors (15053923).

21718557 is a wasteful number, since it uses less digits than its factorization.

21718557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 114929 (or 114923 counting only the distinct ones).

The product of its digits is 19600, while the sum is 36.

The square root of 21718557 is about 4660.3172638781. The cubic root of 21718557 is about 279.0039310349.

The spelling of 21718557 in words is "twenty-one million, seven hundred eighteen thousand, five hundred fifty-seven".