20345640 has 128 divisors (see below), whose sum is σ = 71228160. Its totient is φ = 4552704.

The previous prime is 20345629. The next prime is 20345659. The reversal of 20345640 is 4654302.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 20345640.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 44292 + ... + 44748.

It is an arithmetic number, because the mean of its divisors is an integer number (556470).

Almost surely, 2^20345640 is an apocalyptic number.

20345640 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 20345640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35614080).

20345640 is an abundant number, since it is smaller than the sum of its proper divisors (50882520).

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

20345640 is a wasteful number, since it uses less digits than its factorization.

20345640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 531 (or 527 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 24.

The square root of 20345640 is about 4510.6141488715. The cubic root of 20345640 is about 272.9965247984.

Adding to 20345640 its reverse (4654302), we get a palindrome (24999942).

The spelling of 20345640 in words is "twenty million, three hundred forty-five thousand, six hundred forty".