640400730 has 64 divisors (see below), whose sum is σ = 1642975488. Its totient is φ = 159357440.

The previous prime is 640400729. The next prime is 640400731. The reversal of 640400730 is 37004046.

It is an interprime number because it is at equal distance from previous prime (640400729) and next prime (640400731).

It is a super-2 number, since 2×640400730² = 820226189969065800, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 640400730.

It is not an unprimeable number, because it can be changed into a prime (640400731) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 16972 + ... + 39608.

It is an arithmetic number, because the mean of its divisors is an integer number (25671492).

Almost surely, 2^640400730 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640400730, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (821487744).

640400730 is an abundant number, since it is smaller than the sum of its proper divisors (1002574758).

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

640400730 is a wasteful number, since it uses less digits than its factorization.

640400730 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22711.

The product of its (nonzero) digits is 2016, while the sum is 24.

The square root of 640400730 is about 25306.1401639997. The cubic root of 640400730 is about 861.9537023636.

Adding to 640400730 its reverse (37004046), we get a palindrome (677404776).

The spelling of 640400730 in words is "six hundred forty million, four hundred thousand, seven hundred thirty".