20645851 has 4 divisors (see below), whose sum is σ = 20655000. Its totient is φ = 20636704.

The previous prime is 20645843. The next prime is 20645857. The reversal of 20645851 is 15854602.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 15854602 = 2 ⋅7927301.

It is a cyclic number.

It is not a de Polignac number, because 20645851 - 2³ = 20645843 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20645857) 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, 1500 + ... + 6598.

It is an arithmetic number, because the mean of its divisors is an integer number (5163750).

Almost surely, 2^20645851 is an apocalyptic number.

20645851 is a deficient number, since it is larger than the sum of its proper divisors (9149).

20645851 is an equidigital number, since it uses as much as digits as its factorization.

20645851 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9148.

The product of its (nonzero) digits is 9600, while the sum is 31.

The square root of 20645851 is about 4543.7705707925. The cubic root of 20645851 is about 274.3327116088.

The spelling of 20645851 in words is "twenty million, six hundred forty-five thousand, eight hundred fifty-one".