64781891 has 8 divisors (see below), whose sum is σ = 66070368. Its totient is φ = 63516600.

The previous prime is 64781881. The next prime is 64781921. The reversal of 64781891 is 19818746.

It is not a de Polignac number, because 64781891 - 2¹⁸ = 64519747 is a prime.

It is a Duffinian number.

Its product of digits (96768) is a multiple of the sum of its prime divisors (252).

It is not an unprimeable number, because it can be changed into a prime (64781851) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 357821 + ... + 358001.

It is an arithmetic number, because the mean of its divisors is an integer number (8258796).

Almost surely, 2^64781891 is an apocalyptic number.

64781891 is a deficient number, since it is larger than the sum of its proper divisors (1288477).

64781891 is an frugal number, since it uses more digits than its factorization.

64781891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 394 (or 252 counting only the distinct ones).

The product of its digits is 96768, while the sum is 44.

The square root of 64781891 is about 8048.7198360982. The cubic root of 64781891 is about 401.6223506334.

The spelling of 64781891 in words is "sixty-four million, seven hundred eighty-one thousand, eight hundred ninety-one".