20661280 has 48 divisors (see below), whose sum is σ = 49097664. Its totient is φ = 8216320.

The previous prime is 20661257. The next prime is 20661287. The reversal of 20661280 is 8216602.

It is not an unprimeable number, because it can be changed into a prime (20661287) 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, 41835 + ... + 42325.

It is an arithmetic number, because the mean of its divisors is an integer number (1022868).

Almost surely, 2^20661280 is an apocalyptic number.

20661280 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 20661280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24548832).

20661280 is an abundant number, since it is smaller than the sum of its proper divisors (28436384).

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

20661280 is a wasteful number, since it uses less digits than its factorization.

20661280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 769 (or 761 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 25.

The square root of 20661280 is about 4545.4680727071. The cubic root of 20661280 is about 274.4010324457.

Adding to 20661280 its reverse (8216602), we get a palindrome (28877882).

The spelling of 20661280 in words is "twenty million, six hundred sixty-one thousand, two hundred eighty".