21636140 has 24 divisors (see below), whose sum is σ = 46902912. Its totient is φ = 8375040.

The previous prime is 21636107. The next prime is 21636143. The reversal of 21636140 is 4163612.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21636143) 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, 16829 + ... + 18068.

It is an arithmetic number, because the mean of its divisors is an integer number (1954288).

Almost surely, 2^21636140 is an apocalyptic number.

21636140 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21636140 is an abundant number, since it is smaller than the sum of its proper divisors (25266772).

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

21636140 is a wasteful number, since it uses less digits than its factorization.

21636140 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34937 (or 34935 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 23.

The square root of 21636140 is about 4651.4664354373. The cubic root of 21636140 is about 278.6505647872.

Adding to 21636140 its reverse (4163612), we get a palindrome (25799752).

The spelling of 21636140 in words is "twenty-one million, six hundred thirty-six thousand, one hundred forty".