20705639 has 2 divisors, whose sum is σ = 20705640. Its totient is φ = 20705638.

The previous prime is 20705621. The next prime is 20705651. The reversal of 20705639 is 93650702.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20705639 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20705539) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10352819 + 10352820.

It is an arithmetic number, because the mean of its divisors is an integer number (10352820).

Almost surely, 2^20705639 is an apocalyptic number.

20705639 is a deficient number, since it is larger than the sum of its proper divisors (1).

20705639 is an equidigital number, since it uses as much as digits as its factorization.

20705639 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 11340, while the sum is 32.

The square root of 20705639 is about 4550.3449319804. The cubic root of 20705639 is about 274.5972683472.

The spelling of 20705639 in words is "twenty million, seven hundred five thousand, six hundred thirty-nine".