21633140 has 12 divisors (see below), whose sum is σ = 45429636. Its totient is φ = 8653248.

The previous prime is 21633127. The next prime is 21633149. The reversal of 21633140 is 4133612.

It can be written as a sum of positive squares in 2 ways, for example, as 12645136 + 8988004 = 3556^2 + 2998^2 .

It is a Harshad number since it is a multiple of its sum of digits (20), and also a Moran number because the ratio is a prime number: 1081657 = 21633140 / (2 + 1 + 6 + 3 + 3 + 1 + 4 + 0).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21633149) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 540809 + ... + 540848.

It is an arithmetic number, because the mean of its divisors is an integer number (3785803).

Almost surely, 2^21633140 is an apocalyptic number.

21633140 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21633140 is an abundant number, since it is smaller than the sum of its proper divisors (23796496).

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

21633140 is a wasteful number, since it uses less digits than its factorization.

21633140 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1081666 (or 1081664 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 20.

The square root of 21633140 is about 4651.1439453107. The cubic root of 21633140 is about 278.6376852512.

Adding to 21633140 its reverse (4133612), we get a palindrome (25766752).

The spelling of 21633140 in words is "twenty-one million, six hundred thirty-three thousand, one hundred forty".