1667591861 has 4 divisors (see below), whose sum is σ = 1795868172. Its totient is φ = 1539315552.

The previous prime is 1667591857. The next prime is 1667591881. The reversal of 1667591861 is 1681957661.

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

It can be written as a sum of positive squares in 2 ways, for example, as 473889361 + 1193702500 = 21769^2 + 34550^2 .

It is a cyclic number.

It is not a de Polignac number, because 1667591861 - 2² = 1667591857 is a prime.

It is a super-2 number, since 2×1667591861² = 5561725229746886642, 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 (1667591851) 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, 64138136 + ... + 64138161.

It is an arithmetic number, because the mean of its divisors is an integer number (448967043).

Almost surely, 2^1667591861 is an apocalyptic number.

It is an amenable number.

1667591861 is a deficient number, since it is larger than the sum of its proper divisors (128276311).

1667591861 is a wasteful number, since it uses less digits than its factorization.

1667591861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128276310.

The product of its digits is 544320, while the sum is 50.

The square root of 1667591861 is about 40836.1587444265. The cubic root of 1667591861 is about 1185.8504487492.

The spelling of 1667591861 in words is "one billion, six hundred sixty-seven million, five hundred ninety-one thousand, eight hundred sixty-one".