20646840 has 128 divisors (see below), whose sum is σ = 68040000. Its totient is φ = 4988928.

The previous prime is 20646833. The next prime is 20646841. The reversal of 20646840 is 4864602.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 20646798 and 20646807.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20646841) 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 31 ways as a sum of consecutive naturals, for example, 58986 + ... + 59334.

Almost surely, 2^20646840 is an apocalyptic number.

20646840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20646840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34020000).

20646840 is an abundant number, since it is smaller than the sum of its proper divisors (47393160).

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

20646840 is a wasteful number, since it uses less digits than its factorization.

20646840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 409 (or 405 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 30.

The square root of 20646840 is about 4543.8793998081. The cubic root of 20646840 is about 274.3370920001.

The spelling of 20646840 in words is "twenty million, six hundred forty-six thousand, eight hundred forty".