21211840 has 56 divisors (see below), whose sum is σ = 54406800. Its totient is φ = 7830528.

The previous prime is 21211831. The next prime is 21211849. The reversal of 21211840 is 4811212.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21211831) and next prime (21211849).

It is not an unprimeable number, because it can be changed into a prime (21211849) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1611 + ... + 6709.

It is an arithmetic number, because the mean of its divisors is an integer number (971550).

Almost surely, 2^21211840 is an apocalyptic number.

21211840 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 21211840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27203400).

21211840 is an abundant number, since it is smaller than the sum of its proper divisors (33194960).

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

21211840 is a wasteful number, since it uses less digits than its factorization.

21211840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5129 (or 5119 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 19.

The square root of 21211840 is about 4605.6313356586. The cubic root of 21211840 is about 276.8170147804.

The spelling of 21211840 in words is "twenty-one million, two hundred eleven thousand, eight hundred forty".