21765380 has 48 divisors (see below), whose sum is σ = 56259840. Its totient is φ = 6887808.

The previous prime is 21765347. The next prime is 21765391. The reversal of 21765380 is 8356712.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4160 + ... + 7799.

It is an arithmetic number, because the mean of its divisors is an integer number (1172080).

Almost surely, 2^21765380 is an apocalyptic number.

21765380 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21765380 is an abundant number, since it is smaller than the sum of its proper divisors (34494460).

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

21765380 is a wasteful number, since it uses less digits than its factorization.

21765380 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11988 (or 11986 counting only the distinct ones).

The product of its (nonzero) digits is 10080, while the sum is 32.

The square root of 21765380 is about 4665.3381442292. The cubic root of 21765380 is about 279.2042884868.

The spelling of 21765380 in words is "twenty-one million, seven hundred sixty-five thousand, three hundred eighty".