640406539 has 2 divisors, whose sum is σ = 640406540. Its totient is φ = 640406538.

The previous prime is 640406527. The next prime is 640406563. The reversal of 640406539 is 935604046.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 640406539 - 2¹¹ = 640404491 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 640406498 and 640406507.

It is not a weakly prime, because it can be changed into another prime (640406509) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320203269 + 320203270.

It is an arithmetic number, because the mean of its divisors is an integer number (320203270).

Almost surely, 2^640406539 is an apocalyptic number.

640406539 is a deficient number, since it is larger than the sum of its proper divisors (1).

640406539 is an equidigital number, since it uses as much as digits as its factorization.

640406539 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 77760, while the sum is 37.

The square root of 640406539 is about 25306.2549382559. The cubic root of 640406539 is about 861.9563085827.

The spelling of 640406539 in words is "six hundred forty million, four hundred six thousand, five hundred thirty-nine".