640420111 has 4 divisors (see below), whose sum is σ = 641604424. Its totient is φ = 639235800.

The previous prime is 640420091. The next prime is 640420139. The reversal of 640420111 is 111024046.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 640420111 - 2²¹ = 638322959 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640420171) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 591345 + ... + 592426.

It is an arithmetic number, because the mean of its divisors is an integer number (160401106).

Almost surely, 2^640420111 is an apocalyptic number.

640420111 is a deficient number, since it is larger than the sum of its proper divisors (1184313).

640420111 is a wasteful number, since it uses less digits than its factorization.

640420111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1184312.

The product of its (nonzero) digits is 192, while the sum is 19.

The square root of 640420111 is about 25306.5230918829. The cubic root of 640420111 is about 861.9623976254.

Adding to 640420111 its reverse (111024046), we get a palindrome (751444157).

The spelling of 640420111 in words is "six hundred forty million, four hundred twenty thousand, one hundred eleven".