21718872 has 48 divisors (see below), whose sum is σ = 67226640. Its totient is φ = 6205248.

The previous prime is 21718871. The next prime is 21718891. The reversal of 21718872 is 27881712.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21718871) 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, 21043 + ... + 22050.

It is an arithmetic number, because the mean of its divisors is an integer number (1400555).

Almost surely, 2^21718872 is an apocalyptic number.

It is an amenable number.

21718872 is an abundant number, since it is smaller than the sum of its proper divisors (45507768).

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

21718872 is a wasteful number, since it uses less digits than its factorization.

21718872 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43112 (or 43105 counting only the distinct ones).

The product of its digits is 12544, while the sum is 36.

The square root of 21718872 is about 4660.3510597379. The cubic root of 21718872 is about 279.0052798939.

The spelling of 21718872 in words is "twenty-one million, seven hundred eighteen thousand, eight hundred seventy-two".