640249547 has 4 divisors (see below), whose sum is σ = 731713776. Its totient is φ = 548785320.

The previous prime is 640249537. The next prime is 640249579. The reversal of 640249547 is 745942046.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-640249547 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640249537) 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, 45732104 + ... + 45732117.

It is an arithmetic number, because the mean of its divisors is an integer number (182928444).

Almost surely, 2^640249547 is an apocalyptic number.

640249547 is a deficient number, since it is larger than the sum of its proper divisors (91464229).

640249547 is an equidigital number, since it uses as much as digits as its factorization.

640249547 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 91464228.

The product of its (nonzero) digits is 241920, while the sum is 41.

The square root of 640249547 is about 25303.1529063079. The cubic root of 640249547 is about 861.8858682734.

The spelling of 640249547 in words is "six hundred forty million, two hundred forty-nine thousand, five hundred forty-seven".