20646661 has 4 divisors (see below), whose sum is σ = 23596192.
Its totient is φ = 17697132.
The previous prime is 20646631. The next prime is 20646667. The reversal of 20646661 is 16664602.
It is a semiprime because it is the product of two primes.
It is a cyclic number.
It is not a de Polignac number, because 20646661 - 213 = 20638469 is a prime.
It is a super-2 number, since 2×206466612 = 852569220897842, 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 (20646667) 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 3 ways as a sum of consecutive naturals, for example, 1474755 + ... + 1474768.
It is an arithmetic number, because the mean of its divisors is an integer number (5899048).
Almost surely, 220646661 is an apocalyptic number.
It is an amenable number.
20646661 is a deficient number, since it is larger than the sum of its proper divisors (2949531).
20646661 is an equidigital number, since it uses as much as digits as its factorization.
20646661 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 2949530.
The product of its (nonzero) digits is 10368, while the sum is 31.
The square root of 20646661 is about 4543.8597029398.
The cubic root of 20646661 is about 274.3362991995.
The spelling of 20646661 in words is "twenty million, six hundred forty-six thousand, six hundred sixty-one".