21642816 has 168 divisors, whose sum is σ = 66934080. Its totient is φ = 6150144.

The previous prime is 21642799. The next prime is 21642833. The reversal of 21642816 is 61824612.

It is an interprime number because it is at equal distance from previous prime (21642799) and next prime (21642833).

It is a super-2 number, since 2×21642816² = 936822968819712, which contains 22 as substring.

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

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 746290 + ... + 746318.

Almost surely, 2^21642816 is an apocalyptic number.

21642816 is a gapful number since it is divisible by the number (26) 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 21642816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33467040).

21642816 is an abundant number, since it is smaller than the sum of its proper divisors (45291264).

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

21642816 is a wasteful number, since it uses less digits than its factorization.

21642816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 93 (or 70 counting only the distinct ones).

The product of its digits is 4608, while the sum is 30.

The square root of 21642816 is about 4652.1840032398. The cubic root of 21642816 is about 278.6792217761.

The spelling of 21642816 in words is "twenty-one million, six hundred forty-two thousand, eight hundred sixteen".