20172640 has 24 divisors (see below), whose sum is σ = 47658240. Its totient is φ = 8068992.

The previous prime is 20172637. The next prime is 20172641. The reversal of 20172640 is 4627102.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20172641) 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 3 ways as a sum of consecutive naturals, for example, 62880 + ... + 63199.

It is an arithmetic number, because the mean of its divisors is an integer number (1985760).

Almost surely, 2^20172640 is an apocalyptic number.

20172640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20172640 is an abundant number, since it is smaller than the sum of its proper divisors (27485600).

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

20172640 is a wasteful number, since it uses less digits than its factorization.

20172640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 126094 (or 126086 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 22.

The square root of 20172640 is about 4491.3962194400. The cubic root of 20172640 is about 272.2205535246.

Adding to 20172640 its reverse (4627102), we get a palindrome (24799742).

The spelling of 20172640 in words is "twenty million, one hundred seventy-two thousand, six hundred forty".