21634020 has 48 divisors (see below), whose sum is σ = 67307520. Its totient is φ = 5768928.

The previous prime is 21633973. The next prime is 21634021. The reversal of 21634020 is 2043612.

It is a happy number.

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

It is a junction number, because it is equal to n+sod(n) for n = 21633984 and 21634002.

It is not an unprimeable number, because it can be changed into a prime (21634021) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19492 + ... + 20571.

It is an arithmetic number, because the mean of its divisors is an integer number (1402240).

Almost surely, 2^21634020 is an apocalyptic number.

21634020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21634020 is an abundant number, since it is smaller than the sum of its proper divisors (45673500).

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

21634020 is a wasteful number, since it uses less digits than its factorization.

21634020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40081 (or 40073 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 21634020 is about 4651.2385447319. The cubic root of 21634020 is about 278.6414633718.

Adding to 21634020 its reverse (2043612), we get a palindrome (23677632).

The spelling of 21634020 in words is "twenty-one million, six hundred thirty-four thousand, twenty".