20669840 has 20 divisors (see below), whose sum is σ = 48057564. Its totient is φ = 8267904.

The previous prime is 20669833. The next prime is 20669843. The reversal of 20669840 is 4896602.

It can be written as a sum of positive squares in 2 ways, for example, as 6801664 + 13868176 = 2608^2 + 3724^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a hoax number, since the sum of its digits (35) coincides with the sum of the digits of its distinct prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 20669840.

It is not an unprimeable number, because it can be changed into a prime (20669843) 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, 129107 + ... + 129266.

Almost surely, 2^20669840 is an apocalyptic number.

20669840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20669840 is an abundant number, since it is smaller than the sum of its proper divisors (27387724).

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

20669840 is a wasteful number, since it uses less digits than its factorization.

20669840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 258386 (or 258380 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 35.

The square root of 20669840 is about 4546.4095723989. The cubic root of 20669840 is about 274.4389221365.

The spelling of 20669840 in words is "twenty million, six hundred sixty-nine thousand, eight hundred forty".