21428568 has 192 divisors, whose sum is σ = 73120320. Its totient is φ = 5529600.

The previous prime is 21428549. The next prime is 21428579. The reversal of 21428568 is 86582412.

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

It is a congruent number.

It is an unprimeable number.

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 47 ways as a sum of consecutive naturals, for example, 351258 + ... + 351318.

It is an arithmetic number, because the mean of its divisors is an integer number (380835).

Almost surely, 2^21428568 is an apocalyptic number.

21428568 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

21428568 is the 2928-th heptagonal number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21428568, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36560160).

21428568 is an abundant number, since it is smaller than the sum of its proper divisors (51691752).

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

21428568 is a wasteful number, since it uses less digits than its factorization.

21428568 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138 (or 131 counting only the distinct ones).

The product of its digits is 30720, while the sum is 36.

The square root of 21428568 is about 4629.1001285347. The cubic root of 21428568 is about 277.7565973302.

It can be divided in two parts, 2142 and 8568, that multiplied together give a square (18352656 = 4284²).

The spelling of 21428568 in words is "twenty-one million, four hundred twenty-eight thousand, five hundred sixty-eight".