810642640 has 20 divisors (see below), whose sum is σ = 1884744324. Its totient is φ = 324257024.

The previous prime is 810642631. The next prime is 810642643. The reversal of 810642640 is 46246018.

It can be written as a sum of positive squares in 2 ways, for example, as 317980224 + 492662416 = 17832^2 + 22196^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (810642643) 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, 5066437 + ... + 5066596.

Almost surely, 2^810642640 is an apocalyptic number.

810642640 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

810642640 is an abundant number, since it is smaller than the sum of its proper divisors (1074101684).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

810642640 is a wasteful number, since it uses less digits than its factorization.

810642640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10133046 (or 10133040 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 31.

The square root of 810642640 is about 28471.7867370490. The cubic root of 810642640 is about 932.4162090758.

Adding to 810642640 its reverse (46246018), we get a palindrome (856888658).

The spelling of 810642640 in words is "eight hundred ten million, six hundred forty-two thousand, six hundred forty".