671817781 has 6 divisors (see below), whose sum is σ = 713661410. Its totient is φ = 632298816.

The previous prime is 671817779. The next prime is 671817847. The reversal of 671817781 is 187718176.

It can be written as a sum of positive squares in 3 ways, for example, as 138438756 + 533379025 = 11766^2 + 23095^2 .

It is not a de Polignac number, because 671817781 - 2¹ = 671817779 is a prime.

It is a super-2 number, since 2×671817781² = 902678261735527922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (671817701) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1162026 + ... + 1162603.

Almost surely, 2^671817781 is an apocalyptic number.

It is an amenable number.

671817781 is a deficient number, since it is larger than the sum of its proper divisors (41843629).

671817781 is a wasteful number, since it uses less digits than its factorization.

671817781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2324663 (or 2324646 counting only the distinct ones).

The product of its digits is 131712, while the sum is 46.

The square root of 671817781 is about 25919.4479300775. The cubic root of 671817781 is about 875.8246510192.

The spelling of 671817781 in words is "six hundred seventy-one million, eight hundred seventeen thousand, seven hundred eighty-one".