20666989 has 4 divisors (see below), whose sum is σ = 23619424. Its totient is φ = 17714556.

The previous prime is 20666963. The next prime is 20666999. The reversal of 20666989 is 98966602.

It is a happy number.

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 a cyclic number.

It is not a de Polignac number, because 20666989 - 2¹⁵ = 20634221 is a prime.

It is a super-2 number, since 2×20666989² = 854248868652242, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20666929) 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, 1476207 + ... + 1476220.

It is an arithmetic number, because the mean of its divisors is an integer number (5904856).

Almost surely, 2^20666989 is an apocalyptic number.

It is an amenable number.

20666989 is a deficient number, since it is larger than the sum of its proper divisors (2952435).

20666989 is an equidigital number, since it uses as much as digits as its factorization.

20666989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2952434.

The product of its (nonzero) digits is 279936, while the sum is 46.

The square root of 20666989 is about 4546.0960174638. The cubic root of 20666989 is about 274.4263037298.

The spelling of 20666989 in words is "twenty million, six hundred sixty-six thousand, nine hundred eighty-nine".