166821287 has 4 divisors (see below), whose sum is σ = 167685840. Its totient is φ = 165956736.

The previous prime is 166821269. The next prime is 166821313. The reversal of 166821287 is 782128661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 782128661 = 229 ⋅3415409.

It is a cyclic number.

It is not a de Polignac number, because 166821287 - 2²⁶ = 99712423 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (166821217) 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, 431987 + ... + 432372.

It is an arithmetic number, because the mean of its divisors is an integer number (41921460).

Almost surely, 2^166821287 is an apocalyptic number.

166821287 is a deficient number, since it is larger than the sum of its proper divisors (864553).

166821287 is an equidigital number, since it uses as much as digits as its factorization.

166821287 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 864552.

The product of its digits is 64512, while the sum is 41.

The square root of 166821287 is about 12915.9315188646. The cubic root of 166821287 is about 550.4913372464.

The spelling of 166821287 in words is "one hundred sixty-six million, eight hundred twenty-one thousand, two hundred eighty-seven".