309805813 has 4 divisors (see below), whose sum is σ = 310068000. Its totient is φ = 309543628.

The previous prime is 309805777. The next prime is 309805823. The reversal of 309805813 is 318508903.

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, and also an emirpimes, since its reverse is a distinct semiprime: 318508903 = 233 ⋅1366991.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-309805813 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 (309805823) 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, 129313 + ... + 131686.

It is an arithmetic number, because the mean of its divisors is an integer number (77517000).

Almost surely, 2^309805813 is an apocalyptic number.

It is an amenable number.

309805813 is a deficient number, since it is larger than the sum of its proper divisors (262187).

309805813 is a wasteful number, since it uses less digits than its factorization.

309805813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 262186.

The product of its (nonzero) digits is 25920, while the sum is 37.

The square root of 309805813 is about 17601.3014575627. The cubic root of 309805813 is about 676.6485997695.

The spelling of 309805813 in words is "three hundred nine million, eight hundred five thousand, eight hundred thirteen".