21122740 has 48 divisors (see below), whose sum is σ = 47319552. Its totient is φ = 7901696.

The previous prime is 21122719. The next prime is 21122743. The reversal of 21122740 is 4722112.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21122743) 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, 21132 + ... + 22108.

It is an arithmetic number, because the mean of its divisors is an integer number (985824).

Almost surely, 2^21122740 is an apocalyptic number.

21122740 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 21122740, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23659776).

21122740 is an abundant number, since it is smaller than the sum of its proper divisors (26196812).

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

21122740 is a wasteful number, since it uses less digits than its factorization.

21122740 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1056 (or 1054 counting only the distinct ones).

The product of its (nonzero) digits is 224, while the sum is 19.

The square root of 21122740 is about 4595.9482155481. The cubic root of 21122740 is about 276.4288823197.

Adding to 21122740 its reverse (4722112), we get a palindrome (25844852).

The spelling of 21122740 in words is "twenty-one million, one hundred twenty-two thousand, seven hundred forty".