20389991 has 2 divisors, whose sum is σ = 20389992. Its totient is φ = 20389990.

The previous prime is 20389951. The next prime is 20390003. The reversal of 20389991 is 19998302.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20389991 - 2⁶ = 20389927 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20389951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10194995 + 10194996.

It is an arithmetic number, because the mean of its divisors is an integer number (10194996).

Almost surely, 2^20389991 is an apocalyptic number.

20389991 is a deficient number, since it is larger than the sum of its proper divisors (1).

20389991 is an equidigital number, since it uses as much as digits as its factorization.

20389991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 34992, while the sum is 41.

The square root of 20389991 is about 4515.5277653891. The cubic root of 20389991 is about 273.1947471492.

The spelling of 20389991 in words is "twenty million, three hundred eighty-nine thousand, nine hundred ninety-one".