21877812 has 72 divisors (see below), whose sum is σ = 61038432. Its totient is φ = 6552000.

The previous prime is 21877811. The next prime is 21877829.

It is a happy number.

21877812 is nontrivially palindromic in base 10.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21877811) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 39723 + ... + 40269.

It is an arithmetic number, because the mean of its divisors is an integer number (847756).

Almost surely, 2^21877812 is an apocalyptic number.

21877812 is a gapful number since it is divisible by the number (22) 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 21877812, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30519216).

21877812 is an abundant number, since it is smaller than the sum of its proper divisors (39160620).

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

21877812 is a wasteful number, since it uses less digits than its factorization.

21877812 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 669 (or 664 counting only the distinct ones).

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

The square root of 21877812 is about 4677.3723392520. The cubic root of 21877812 is about 279.6842188290.

It can be divided in two parts, 2187 and 7812, that added together give a palindrome (9999).

The spelling of 21877812 in words is "twenty-one million, eight hundred seventy-seven thousand, eight hundred twelve".