309920645 has 6 divisors (see below), whose sum is σ = 371952018. Its totient is φ = 247905024.

The previous prime is 309920641. The next prime is 309920657. The reversal of 309920645 is 546029903.

It can be written as a sum of positive squares in 3 ways, for example, as 25020004 + 284900641 = 5002^2 + 16879^2 .

It is not a de Polignac number, because 309920645 - 2² = 309920641 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 309920599 and 309920608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (309920641) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 35429 + ... + 43301.

It is an arithmetic number, because the mean of its divisors is an integer number (61992003).

Almost surely, 2^309920645 is an apocalyptic number.

It is an amenable number.

309920645 is a deficient number, since it is larger than the sum of its proper divisors (62031373).

309920645 is an frugal number, since it uses more digits than its factorization.

309920645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15751 (or 7878 counting only the distinct ones).

The product of its (nonzero) digits is 58320, while the sum is 38.

The square root of 309920645 is about 17604.5631868558. The cubic root of 309920645 is about 676.7321911791.

Multiplying 309920645 by its product of nonzero digits (58320), we get a square (18074572016400 = 4251420²).

The spelling of 309920645 in words is "three hundred nine million, nine hundred twenty thousand, six hundred forty-five".