20135640 has 64 divisors (see below), whose sum is σ = 69039360. Its totient is φ = 4602240.

The previous prime is 20135629. The next prime is 20135641. The reversal of 20135640 is 4653102.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20135641) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11146 + ... + 12825.

It is an arithmetic number, because the mean of its divisors is an integer number (1078740).

Almost surely, 2^20135640 is an apocalyptic number.

20135640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20135640 is an abundant number, since it is smaller than the sum of its proper divisors (48903720).

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

20135640 is a wasteful number, since it uses less digits than its factorization.

20135640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23992 (or 23988 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 20135640 is about 4487.2753425659. The cubic root of 20135640 is about 272.0540189713.

Adding to 20135640 its reverse (4653102), we get a palindrome (24788742).

The spelling of 20135640 in words is "twenty million, one hundred thirty-five thousand, six hundred forty".