21718356 has 48 divisors (see below), whose sum is σ = 56645568. Its totient is φ = 6419200.

The previous prime is 21718351. The next prime is 21718363. The reversal of 21718356 is 65381712.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21718351) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3406 + ... + 7418.

It is an arithmetic number, because the mean of its divisors is an integer number (1180116).

Almost surely, 2^21718356 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21718356, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28322784).

21718356 is an abundant number, since it is smaller than the sum of its proper divisors (34927212).

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

21718356 is a wasteful number, since it uses less digits than its factorization.

21718356 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4072 (or 4070 counting only the distinct ones).

The product of its digits is 10080, while the sum is 33.

The square root of 21718356 is about 4660.2956987728. The cubic root of 21718356 is about 279.0030703276.

The spelling of 21718356 in words is "twenty-one million, seven hundred eighteen thousand, three hundred fifty-six".