640402026 has 32 divisors (see below), whose sum is σ = 1398905856. Its totient is φ = 193830000.

The previous prime is 640401977. The next prime is 640402027. The reversal of 640402026 is 620204046.

It is a super-2 number, since 2×640402026² = 820229509809809352, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 640401987 and 640402005.

It is not an unprimeable number, because it can be changed into a prime (640402027) 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, 54801 + ... + 65451.

It is an arithmetic number, because the mean of its divisors is an integer number (43715808).

Almost surely, 2^640402026 is an apocalyptic number.

640402026 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

640402026 is an abundant number, since it is smaller than the sum of its proper divisors (758503830).

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

640402026 is a wasteful number, since it uses less digits than its factorization.

640402026 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11578.

The product of its (nonzero) digits is 2304, while the sum is 24.

The square root of 640402026 is about 25306.1657704205. The cubic root of 640402026 is about 861.9542838178.

It can be divided in two parts, 6404020 and 26, that added together give a palindrome (6404046).

The spelling of 640402026 in words is "six hundred forty million, four hundred two thousand, twenty-six".