645861 has 8 divisors (see below), whose sum is σ = 864864. Its totient is φ = 428720.

The previous prime is 645857. The next prime is 645877. The reversal of 645861 is 168546.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 645861 - 2² = 645857 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645851) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1150 + ... + 1616.

It is an arithmetic number, because the mean of its divisors is an integer number (108108).

2⁶⁴⁵⁸⁶¹ is an apocalyptic number.

It is an amenable number.

645861 is a deficient number, since it is larger than the sum of its proper divisors (219003).

645861 is a wasteful number, since it uses less digits than its factorization.

645861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 931.

The product of its digits is 5760, while the sum is 30.

The square root of 645861 is about 803.6547766299. The cubic root of 645861 is about 86.4396540798.

The spelling of 645861 in words is "six hundred forty-five thousand, eight hundred sixty-one".