21122640 has 320 divisors, whose sum is σ = 91422720. Its totient is φ = 4354560.

The previous prime is 21122611. The next prime is 21122641. The reversal of 21122640 is 4622112.

21122640 is a `hidden beast` number, since 2 + 1 + 1 + 22 + 640 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21122641) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 166257 + ... + 166383.

It is an arithmetic number, because the mean of its divisors is an integer number (285696).

Almost surely, 2^21122640 is an apocalyptic number.

21122640 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 21122640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (45711360).

21122640 is an abundant number, since it is smaller than the sum of its proper divisors (70300080).

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

21122640 is a wasteful number, since it uses less digits than its factorization.

21122640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 167 (or 155 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 18.

The square root of 21122640 is about 4595.9373363874. The cubic root of 21122640 is about 276.4284460926.

Adding to 21122640 its reverse (4622112), we get a palindrome (25744752).

The spelling of 21122640 in words is "twenty-one million, one hundred twenty-two thousand, six hundred forty".