20391121 has 2 divisors, whose sum is σ = 20391122. Its totient is φ = 20391120.

The previous prime is 20391103. The next prime is 20391131. The reversal of 20391121 is 12119302.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11155600 + 9235521 = 3340^2 + 3039^2 .

It is a cyclic number.

It is not a de Polignac number, because 20391121 - 2⁹ = 20390609 is a prime.

It is not a weakly prime, because it can be changed into another prime (20391101) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10195560 + 10195561.

It is an arithmetic number, because the mean of its divisors is an integer number (10195561).

Almost surely, 2^20391121 is an apocalyptic number.

It is an amenable number.

20391121 is a deficient number, since it is larger than the sum of its proper divisors (1).

20391121 is an equidigital number, since it uses as much as digits as its factorization.

20391121 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 108, while the sum is 19.

The square root of 20391121 is about 4515.6528874571. The cubic root of 20391121 is about 273.1997938142.

It can be divided in two parts, 2039 and 1121, that added together give a triangular number (3160 = T₇₉).

The spelling of 20391121 in words is "twenty million, three hundred ninety-one thousand, one hundred twenty-one".