20663261 has 4 divisors (see below), whose sum is σ = 20674332. Its totient is φ = 20652192.

The previous prime is 20663257. The next prime is 20663273. The reversal of 20663261 is 16236602.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 3976036 + 16687225 = 1994^2 + 4085^2 .

It is a cyclic number.

It is not a de Polignac number, because 20663261 - 2² = 20663257 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20663261.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20663761) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1970 + ... + 6723.

It is an arithmetic number, because the mean of its divisors is an integer number (5168583).

Almost surely, 2^20663261 is an apocalyptic number.

It is an amenable number.

20663261 is a deficient number, since it is larger than the sum of its proper divisors (11071).

20663261 is an equidigital number, since it uses as much as digits as its factorization.

20663261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11070.

The product of its (nonzero) digits is 2592, while the sum is 26.

The square root of 20663261 is about 4545.6859768356. The cubic root of 20663261 is about 274.4098020069.

Adding to 20663261 its reverse (16236602), we get a palindrome (36899863).

The spelling of 20663261 in words is "twenty million, six hundred sixty-three thousand, two hundred sixty-one".