21378180 has 48 divisors (see below), whose sum is σ = 63383040. Its totient is φ = 5365248.

The previous prime is 21378167. The next prime is 21378187. The reversal of 21378180 is 8187312.

It is a happy number.

It is a super-2 number, since 2×21378180² = 914053160224800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21378187) 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, 9460 + ... + 11499.

It is an arithmetic number, because the mean of its divisors is an integer number (1320480).

Almost surely, 2^21378180 is an apocalyptic number.

21378180 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21378180 is an abundant number, since it is smaller than the sum of its proper divisors (42004860).

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

21378180 is a wasteful number, since it uses less digits than its factorization.

21378180 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20988 (or 20986 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 30.

The square root of 21378180 is about 4623.6543988495. The cubic root of 21378180 is about 277.5387171042.

The spelling of 21378180 in words is "twenty-one million, three hundred seventy-eight thousand, one hundred eighty".