640919 has 2 divisors, whose sum is σ = 640920. Its totient is φ = 640918.

The previous prime is 640907. The next prime is 640933. The reversal of 640919 is 919046.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 640919 - 2⁸ = 640663 is a prime.

It is a super-2 number, since 2×640919² = 821554329122, which contains 22 as substring.

It is a Chen prime.

It is an Ulam number.

It is a junction number, because it is equal to n+sod(n) for n = 640891 and 640900.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640949) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320459 + 320460.

It is an arithmetic number, because the mean of its divisors is an integer number (320460).

2⁶⁴⁰⁹¹⁹ is an apocalyptic number.

640919 is a deficient number, since it is larger than the sum of its proper divisors (1).

640919 is an equidigital number, since it uses as much as digits as its factorization.

640919 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1944, while the sum is 29.

The square root of 640919 is about 800.5741689563. The cubic root of 640919 is about 86.2186163211.

It can be divided in two parts, 6409 and 19, that multiplied together give a triangular number (121771 = T₄₉₃).

The spelling of 640919 in words is "six hundred forty thousand, nine hundred nineteen".