21333780 has 120 divisors (see below), whose sum is σ = 72144072. Its totient is φ = 5246208.

The previous prime is 21333779. The next prime is 21333839. The reversal of 21333780 is 8733312.

It can be written as a sum of positive squares in 4 ways, for example, as 1245456 + 20088324 = 1116^2 + 4482^2 .

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 20554 + ... + 21566.

Almost surely, 2^21333780 is an apocalyptic number.

21333780 is a gapful number since it is divisible by the number (20) 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 21333780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36072036).

21333780 is an abundant number, since it is smaller than the sum of its proper divisors (50810292).

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

21333780 is a wasteful number, since it uses less digits than its factorization.

21333780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1047 (or 1036 counting only the distinct ones).

The product of its (nonzero) digits is 3024, while the sum is 27.

The square root of 21333780 is about 4618.8505063490. The cubic root of 21333780 is about 277.3464453603.

The spelling of 21333780 in words is "twenty-one million, three hundred thirty-three thousand, seven hundred eighty".