20006661 has 4 divisors (see below), whose sum is σ = 26675552. Its totient is φ = 13337772.

The previous prime is 20006641. The next prime is 20006663. The reversal of 20006661 is 16660002.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 20006661 - 2⁷ = 20006533 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20006663) 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, 3334441 + ... + 3334446.

It is an arithmetic number, because the mean of its divisors is an integer number (6668888).

Almost surely, 2^20006661 is an apocalyptic number.

It is an amenable number.

20006661 is a deficient number, since it is larger than the sum of its proper divisors (6668891).

20006661 is an equidigital number, since it uses as much as digits as its factorization.

20006661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6668890.

The product of its (nonzero) digits is 432, while the sum is 21.

The square root of 20006661 is about 4472.8806154424. The cubic root of 20006661 is about 271.4718928742.

Adding to 20006661 its reverse (16660002), we get a palindrome (36666663).

The spelling of 20006661 in words is "twenty million, six thousand, six hundred sixty-one".