21655000 has 80 divisors (see below), whose sum is σ = 52295760. Its totient is φ = 8400000.

The previous prime is 21654989. The next prime is 21655001. The reversal of 21655000 is 55612.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21655001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 304965 + ... + 305035.

It is an arithmetic number, because the mean of its divisors is an integer number (653697).

Almost surely, 2^21655000 is an apocalyptic number.

21655000 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 21655000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26147880).

21655000 is an abundant number, since it is smaller than the sum of its proper divisors (30640760).

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

21655000 is an equidigital number, since it uses as much as digits as its factorization.

21655000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 158 (or 139 counting only the distinct ones).

The product of its (nonzero) digits is 300, while the sum is 19.

The square root of 21655000 is about 4653.4933114812. The cubic root of 21655000 is about 278.7315068804.

The spelling of 21655000 in words is "twenty-one million, six hundred fifty-five thousand".