21678336 has 81 divisors (see below), whose sum is σ = 63155001. Its totient is φ = 7151616.

The previous prime is 21678329. The next prime is 21678343. The reversal of 21678336 is 63387612.

21678336 = 1³ + 2³ + ... + 96³.

It is a happy number.

The square root of 21678336 is 4656.

It is a perfect power (a square), and thus also a powerful number.

It is an interprime number because it is at equal distance from previous prime (21678329) and next prime (21678343).

It can be written as a sum of positive squares in only one way, i.e., 9734400 + 11943936 = 3120^2 + 3456^2 .

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

Its product of digits (36288) is a multiple of the sum of its prime factors (216).

It is a self number, because there is not a number n which added to its sum of digits gives 21678336.

It is an unprimeable number.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 223440 + ... + 223536.

Almost surely, 2^21678336 is an apocalyptic number.

21678336 is the 4656-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21678336

21678336 is an abundant number, since it is smaller than the sum of its proper divisors (41476665).

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

21678336 is an frugal number, since it uses more digits than its factorization.

21678336 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 216 (or 102 counting only the distinct ones).

The product of its digits is 36288, while the sum is 36.

The cubic root of 21678336 is about 278.8315937484.

Multiplying 21678336 by its sum of digits (36), we get a square (780420096 = 27936²).

21678336 divided by its sum of digits (36) gives a square (602176 = 776²).

The spelling of 21678336 in words is "twenty-one million, six hundred seventy-eight thousand, three hundred thirty-six".