20661000 has 128 divisors (see below), whose sum is σ = 66044160. Its totient is φ = 5376000.

The previous prime is 20660993. The next prime is 20661013. The reversal of 20661000 is 16602.

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

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 212952 + ... + 213048.

It is an arithmetic number, because the mean of its divisors is an integer number (515970).

Almost surely, 2^20661000 is an apocalyptic number.

20661000 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20661000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33022080).

20661000 is an abundant number, since it is smaller than the sum of its proper divisors (45383160).

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

20661000 is a wasteful number, since it uses less digits than its factorization.

20661000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 192 (or 178 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 15.

The square root of 20661000 is about 4545.4372726945. The cubic root of 20661000 is about 274.3997928866.

Adding to 20661000 its reverse (16602), we get a palindrome (20677602).

The spelling of 20661000 in words is "twenty million, six hundred sixty-one thousand".