21206620 has 24 divisors (see below), whose sum is σ = 44629200. Its totient is φ = 8464512.

The previous prime is 21206617. The next prime is 21206623. The reversal of 21206620 is 2660212.

It is an interprime number because it is at equal distance from previous prime (21206617) and next prime (21206623).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21206623) 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, 12376 + ... + 13984.

It is an arithmetic number, because the mean of its divisors is an integer number (1859550).

Almost surely, 2^21206620 is an apocalyptic number.

21206620 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21206620 is an abundant number, since it is smaller than the sum of its proper divisors (23422580).

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

21206620 is a wasteful number, since it uses less digits than its factorization.

21206620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2277 (or 2275 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 19.

The square root of 21206620 is about 4605.0646032385. The cubic root of 21206620 is about 276.7943057122.

Adding to 21206620 its reverse (2660212), we get a palindrome (23866832).

The spelling of 21206620 in words is "twenty-one million, two hundred six thousand, six hundred twenty".