21800180 has 48 divisors (see below), whose sum is σ = 47246976. Its totient is φ = 8446080.

The previous prime is 21800131. The next prime is 21800189. The reversal of 21800180 is 8100812.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21800189) 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, 130457 + ... + 130623.

It is an arithmetic number, because the mean of its divisors is an integer number (984312).

Almost surely, 2^21800180 is an apocalyptic number.

21800180 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21800180 is an abundant number, since it is smaller than the sum of its proper divisors (25446796).

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

21800180 is a wasteful number, since it uses less digits than its factorization.

21800180 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 344 (or 342 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 20.

The square root of 21800180 is about 4669.0662878139. The cubic root of 21800180 is about 279.3530129820.

Adding to 21800180 its reverse (8100812), we get a palindrome (29900992).

The spelling of 21800180 in words is "twenty-one million, eight hundred thousand, one hundred eighty".