20691439 has 2 divisors, whose sum is σ = 20691440. Its totient is φ = 20691438.

The previous prime is 20691403. The next prime is 20691457. The reversal of 20691439 is 93419602.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20691439 - 2⁷ = 20691311 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20691469) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10345719 + 10345720.

It is an arithmetic number, because the mean of its divisors is an integer number (10345720).

Almost surely, 2^20691439 is an apocalyptic number.

20691439 is a deficient number, since it is larger than the sum of its proper divisors (1).

20691439 is an equidigital number, since it uses as much as digits as its factorization.

20691439 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 11664, while the sum is 34.

The square root of 20691439 is about 4548.7843430965. The cubic root of 20691439 is about 274.5344807344.

The spelling of 20691439 in words is "twenty million, six hundred ninety-one thousand, four hundred thirty-nine".