21117628 has 36 divisors (see below), whose sum is σ = 43318632. Its totient is φ = 8981280.

The previous prime is 21117563. The next prime is 21117631. The reversal of 21117628 is 82671112.

It is a super-3 number, since 3×21117628³ (a number of 23 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a junction number, because it is equal to n+sod(n) for n = 21117596 and 21117605.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 31618 + ... + 32278.

Almost surely, 2^21117628 is an apocalyptic number.

21117628 is a gapful number since it is divisible by the number (28) 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 21117628, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21659316).

21117628 is an abundant number, since it is smaller than the sum of its proper divisors (22201004).

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

21117628 is a wasteful number, since it uses less digits than its factorization.

21117628 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 842 (or 833 counting only the distinct ones).

The product of its digits is 1344, while the sum is 28.

The square root of 21117628 is about 4595.3920398591. The cubic root of 21117628 is about 276.4065806287.

It can be divided in two parts, 21 and 117628, that added together give a 6-th power (117649 = 7⁶).

The spelling of 21117628 in words is "twenty-one million, one hundred seventeen thousand, six hundred twenty-eight".