640897773 has 16 divisors (see below), whose sum is σ = 926868096. Its totient is φ = 392322560.

The previous prime is 640897771. The next prime is 640897787. The reversal of 640897773 is 377798046.

It is a cyclic number.

It is not a de Polignac number, because 640897773 - 2¹ = 640897771 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (51).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640897771) 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, 151161 + ... + 155342.

It is an arithmetic number, because the mean of its divisors is an integer number (57929256).

Almost surely, 2^640897773 is an apocalyptic number.

It is an amenable number.

640897773 is a deficient number, since it is larger than the sum of its proper divisors (285970323).

640897773 is a wasteful number, since it uses less digits than its factorization.

640897773 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 306564.

The product of its (nonzero) digits is 1778112, while the sum is 51.

The square root of 640897773 is about 25315.9588599761. The cubic root of 640897773 is about 862.1766446772.

The spelling of 640897773 in words is "six hundred forty million, eight hundred ninety-seven thousand, seven hundred seventy-three".