20621220 has 24 divisors (see below), whose sum is σ = 57739584. Its totient is φ = 5498976.

The previous prime is 20621191. The next prime is 20621239. The reversal of 20621220 is 2212602.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 20621220.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 171784 + ... + 171903.

It is an arithmetic number, because the mean of its divisors is an integer number (2405816).

Almost surely, 2^20621220 is an apocalyptic number.

20621220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20621220 is an abundant number, since it is smaller than the sum of its proper divisors (37118364).

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

20621220 is a wasteful number, since it uses less digits than its factorization.

20621220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 343699 (or 343697 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 15.

The square root of 20621220 is about 4541.0593477734. The cubic root of 20621220 is about 274.2235730071.

Adding to 20621220 its reverse (2212602), we get a palindrome (22833822).

The spelling of 20621220 in words is "twenty million, six hundred twenty-one thousand, two hundred twenty".