21735780 has 48 divisors (see below), whose sum is σ = 66394944. Its totient is φ = 5269120.

The previous prime is 21735751. The next prime is 21735787. The reversal of 21735780 is 8753712.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is not an unprimeable number, because it can be changed into a prime (21735787) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15807 + ... + 17126.

It is an arithmetic number, because the mean of its divisors is an integer number (1383228).

Almost surely, 2^21735780 is an apocalyptic number.

21735780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21735780 is an abundant number, since it is smaller than the sum of its proper divisors (44659164).

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

21735780 is a wasteful number, since it uses less digits than its factorization.

21735780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32956 (or 32954 counting only the distinct ones).

The product of its (nonzero) digits is 11760, while the sum is 33.

The square root of 21735780 is about 4662.1647332543. The cubic root of 21735780 is about 279.0776623768.

The spelling of 21735780 in words is "twenty-one million, seven hundred thirty-five thousand, seven hundred eighty".