21878100 has 180 divisors, whose sum is σ = 73834684. Its totient is φ = 5598720.

The previous prime is 21878089. The next prime is 21878111. The reversal of 21878100 is 187812.

It is an interprime number because it is at equal distance from previous prime (21878089) and next prime (21878111).

It can be written as a sum of positive squares in 6 ways, for example, as 311364 + 21566736 = 558^2 + 4644^2 .

It is a tau number, because it is divible by the number of its divisors (180).

It is a super-2 number, since 2×21878100² = 957302519220000, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

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 59 ways as a sum of consecutive naturals, for example, 299664 + ... + 299736.

Almost surely, 2^21878100 is an apocalyptic number.

21878100 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 21878100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36917342).

21878100 is an abundant number, since it is smaller than the sum of its proper divisors (51956584).

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

21878100 is a wasteful number, since it uses less digits than its factorization.

21878100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 136 (or 120 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 27.

The square root of 21878100 is about 4677.4031256671. The cubic root of 21878100 is about 279.6854460800.

The spelling of 21878100 in words is "twenty-one million, eight hundred seventy-eight thousand, one hundred".