20720345 has 4 divisors (see below), whose sum is σ = 24864420. Its totient is φ = 16576272.

The previous prime is 20720341. The next prime is 20720347. The reversal of 20720345 is 54302702.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 54302702 = 2 ⋅27151351.

It can be written as a sum of positive squares in 2 ways, for example, as 11744329 + 8976016 = 3427^2 + 2996^2 .

It is a cyclic number.

It is not a de Polignac number, because 20720345 - 2² = 20720341 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20720345.

It is not an unprimeable number, because it can be changed into a prime (20720341) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2072030 + ... + 2072039.

It is an arithmetic number, because the mean of its divisors is an integer number (6216105).

Almost surely, 2^20720345 is an apocalyptic number.

It is an amenable number.

20720345 is a deficient number, since it is larger than the sum of its proper divisors (4144075).

20720345 is an equidigital number, since it uses as much as digits as its factorization.

20720345 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4144074.

The product of its (nonzero) digits is 1680, while the sum is 23.

The square root of 20720345 is about 4551.9605666130. The cubic root of 20720345 is about 274.6622630694.

The spelling of 20720345 in words is "twenty million, seven hundred twenty thousand, three hundred forty-five".