20866644 has 18 divisors (see below), whose sum is σ = 52746330. Its totient is φ = 6955536.

The previous prime is 20866639. The next prime is 20866649. The reversal of 20866644 is 44666802.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (20866639) and next prime (20866649).

It can be written as a sum of positive squares in only one way, i.e., 20520900 + 345744 = 4530^2 + 588^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 579629 = 20866644 / (2 + 0 + 8 + 6 + 6 + 6 + 4 + 4).

It is a junction number, because it is equal to n+sod(n) for n = 20866599 and 20866608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20866649) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 289779 + ... + 289850.

Almost surely, 2^20866644 is an apocalyptic number.

It is an amenable number.

20866644 is an abundant number, since it is smaller than the sum of its proper divisors (31879686).

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

20866644 is a wasteful number, since it uses less digits than its factorization.

20866644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 579639 (or 579634 counting only the distinct ones).

The product of its (nonzero) digits is 55296, while the sum is 36.

The square root of 20866644 is about 4568.0021891413. The cubic root of 20866644 is about 275.3071785130.

The spelling of 20866644 in words is "twenty million, eight hundred sixty-six thousand, six hundred forty-four".