21877856 has 96 divisors (see below), whose sum is σ = 57915648. Its totient is φ = 7856640.

The previous prime is 21877837. The next prime is 21877859. The reversal of 21877856 is 65877812.

21877856 = T₇₁₅ + T₇₁₆ + ... + T₇₉₁.

It is a Harshad number since it is a multiple of its sum of digits (44).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21877859) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 31691 + ... + 32373.

It is an arithmetic number, because the mean of its divisors is an integer number (603288).

Almost surely, 2^21877856 is an apocalyptic number.

21877856 is a gapful number since it is divisible by the number (26) 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 21877856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28957824).

21877856 is an abundant number, since it is smaller than the sum of its proper divisors (36037792).

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

21877856 is a wasteful number, since it uses less digits than its factorization.

21877856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 724 (or 716 counting only the distinct ones).

The product of its digits is 188160, while the sum is 44.

The square root of 21877856 is about 4677.3770427452. The cubic root of 21877856 is about 279.6844063264.

Subtracting from 21877856 its sum of digits (44), we obtain a palindrome (21877812).

The spelling of 21877856 in words is "twenty-one million, eight hundred seventy-seven thousand, eight hundred fifty-six".