20661290 has 32 divisors (see below), whose sum is σ = 42411600. Its totient is φ = 7179264.

The previous prime is 20661287. The next prime is 20661299. The reversal of 20661290 is 9216602.

It can be written as a sum of positive squares in 8 ways, for example, as 12117361 + 8543929 = 3481^2 + 2923^2 .

It is a Harshad number since it is a multiple of its sum of digits (26).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20661299) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2465 + ... + 6884.

Almost surely, 2^20661290 is an apocalyptic number.

20661290 is an abundant number, since it is smaller than the sum of its proper divisors (21750310).

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

20661290 is a wasteful number, since it uses less digits than its factorization.

20661290 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9386.

The product of its (nonzero) digits is 1296, while the sum is 26.

The square root of 20661290 is about 4545.4691727037. The cubic root of 20661290 is about 274.4010767155.

Adding to 20661290 its reverse (9216602), we get a palindrome (29877892).

The spelling of 20661290 in words is "twenty million, six hundred sixty-one thousand, two hundred ninety".