640402 has 16 divisors (see below), whose sum is σ = 1108800. Its totient is φ = 271728.

The previous prime is 640369. The next prime is 640411. The reversal of 640402 is 204046.

It is a super-2 number, since 2×640402² = 820229443208, which contains 22 as substring.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 640402.

It is an unprimeable number.

640402 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1933 + ... + 2239.

It is an arithmetic number, because the mean of its divisors is an integer number (69300).

2⁶⁴⁰⁴⁰² is an apocalyptic number.

640402 is a deficient number, since it is larger than the sum of its proper divisors (468398).

640402 is a wasteful number, since it uses less digits than its factorization.

640402 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 465.

The product of its (nonzero) digits is 192, while the sum is 16.

The square root of 640402 is about 800.2512105583. The cubic root of 640402 is about 86.1954272153.

Adding to 640402 its reverse (204046), we get a palindrome (844448).

The spelling of 640402 in words is "six hundred forty thousand, four hundred two".