671609981 has 4 divisors (see below), whose sum is σ = 767554272. Its totient is φ = 575665692.

The previous prime is 671609941. The next prime is 671609989. The reversal of 671609981 is 189906176.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 671609981 - 2¹⁰ = 671608957 is a prime.

It is a super-2 number, since 2×671609981² = 902119933157640722, 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 (671609989) 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, 47972135 + ... + 47972148.

It is an arithmetic number, because the mean of its divisors is an integer number (191888568).

Almost surely, 2^671609981 is an apocalyptic number.

It is an amenable number.

671609981 is a deficient number, since it is larger than the sum of its proper divisors (95944291).

671609981 is an equidigital number, since it uses as much as digits as its factorization.

671609981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 95944290.

The product of its (nonzero) digits is 163296, while the sum is 47.

The square root of 671609981 is about 25915.4390470237. The cubic root of 671609981 is about 875.7343412481.

The spelling of 671609981 in words is "six hundred seventy-one million, six hundred nine thousand, nine hundred eighty-one".