21227640 has 128 divisors (see below), whose sum is σ = 74856960. Its totient is φ = 4713984.

The previous prime is 21227629. The next prime is 21227671. The reversal of 21227640 is 4672212.

It is a super-2 number, since 2×21227640² = 901225399939200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 21227640.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 30739 + ... + 31421.

It is an arithmetic number, because the mean of its divisors is an integer number (584820).

Almost surely, 2^21227640 is an apocalyptic number.

21227640 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 21227640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37428480).

21227640 is an abundant number, since it is smaller than the sum of its proper divisors (53629320).

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

21227640 is a wasteful number, since it uses less digits than its factorization.

21227640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 741 (or 737 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 24.

The square root of 21227640 is about 4607.3463078002. The cubic root of 21227640 is about 276.8857283438.

Adding to 21227640 its reverse (4672212), we get a palindrome (25899852).

The spelling of 21227640 in words is "twenty-one million, two hundred twenty-seven thousand, six hundred forty".