21877128 has 240 divisors, whose sum is σ = 78211980. Its totient is φ = 5660928.

The previous prime is 21877109. The next prime is 21877133. The reversal of 21877128 is 82177812.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 21734244 + 142884 = 4662^2 + 378^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a nude number because it is divisible by every one of its digits.

Its product of digits (12544) is a multiple of the sum of its prime factors (98).

It is a junction number, because it is equal to n+sod(n) for n = 21877092 and 21877101.

It is an unprimeable number.

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 59 ways as a sum of consecutive naturals, for example, 412750 + ... + 412802.

Almost surely, 2^21877128 is an apocalyptic number.

21877128 is a gapful number since it is divisible by the number (28) 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 21877128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39105990).

21877128 is an abundant number, since it is smaller than the sum of its proper divisors (56334852).

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

21877128 is a wasteful number, since it uses less digits than its factorization.

21877128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 98 (or 78 counting only the distinct ones).

The product of its digits is 12544, while the sum is 36.

The square root of 21877128 is about 4677.2992207042. The cubic root of 21877128 is about 279.6813040647.

The spelling of 21877128 in words is "twenty-one million, eight hundred seventy-seven thousand, one hundred twenty-eight".