20661804 has 72 divisors (see below), whose sum is σ = 56106960. Its totient is φ = 6640704.

The previous prime is 20661803. The next prime is 20661821. The reversal of 20661804 is 40816602.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (20661803) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 27822 + ... + 28554.

Almost surely, 2^20661804 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20661804, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28053480).

20661804 is an abundant number, since it is smaller than the sum of its proper divisors (35445156).

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

20661804 is a wasteful number, since it uses less digits than its factorization.

20661804 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 781 (or 767 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 27.

The square root of 20661804 is about 4545.5257121702. The cubic root of 20661804 is about 274.4033521621.

The spelling of 20661804 in words is "twenty million, six hundred sixty-one thousand, eight hundred four".