20305891 has 4 divisors (see below), whose sum is σ = 20609032. Its totient is φ = 20002752.

The previous prime is 20305861. The next prime is 20305897. The reversal of 20305891 is 19850302.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20305891 - 2⁹ = 20305379 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20305897) 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, 151470 + ... + 151603.

It is an arithmetic number, because the mean of its divisors is an integer number (5152258).

Almost surely, 2^20305891 is an apocalyptic number.

20305891 is a deficient number, since it is larger than the sum of its proper divisors (303141).

20305891 is an equidigital number, since it uses as much as digits as its factorization.

20305891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 303140.

The product of its (nonzero) digits is 2160, while the sum is 28.

The square root of 20305891 is about 4506.2058319611. The cubic root of 20305891 is about 272.8186256966.

It can be divided in two parts, 2030 and 5891, that added together give a square (7921 = 89²).

The spelling of 20305891 in words is "twenty million, three hundred five thousand, eight hundred ninety-one".