21618872 has 32 divisors (see below), whose sum is σ = 45169920. Its totient is φ = 9615840.

The previous prime is 21618847. The next prime is 21618889. The reversal of 21618872 is 27881612.

It is a Smith number, since the sum of its digits (35) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1523 + ... + 6749.

It is an arithmetic number, because the mean of its divisors is an integer number (1411560).

Almost surely, 2^21618872 is an apocalyptic number.

21618872 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21618872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22584960).

21618872 is an abundant number, since it is smaller than the sum of its proper divisors (23551048).

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

21618872 is a wasteful number, since it uses less digits than its factorization.

21618872 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5291 (or 5287 counting only the distinct ones).

The product of its digits is 10752, while the sum is 35.

The square root of 21618872 is about 4649.6098761079. The cubic root of 21618872 is about 278.5764138740.

The spelling of 21618872 in words is "twenty-one million, six hundred eighteen thousand, eight hundred seventy-two".