20661720 has 32 divisors (see below), whose sum is σ = 61985520. Its totient is φ = 5509760.

The previous prime is 20661703. The next prime is 20661727. The reversal of 20661720 is 2716602.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20661727) by changing a digit.

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, 85971 + ... + 86210.

Almost surely, 2^20661720 is an apocalyptic number.

20661720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20661720 is an abundant number, since it is smaller than the sum of its proper divisors (41323800).

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

20661720 is a wasteful number, since it uses less digits than its factorization.

20661720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 172195 (or 172191 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 24.

The square root of 20661720 is about 4545.5164723054. The cubic root of 20661720 is about 274.4029803018.

The spelling of 20661720 in words is "twenty million, six hundred sixty-one thousand, seven hundred twenty".