20309749 has 2 divisors, whose sum is σ = 20309750. Its totient is φ = 20309748.

The previous prime is 20309701. The next prime is 20309753. The reversal of 20309749 is 94790302.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14516100 + 5793649 = 3810^2 + 2407^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20309749 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20306749) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10154874 + 10154875.

It is an arithmetic number, because the mean of its divisors is an integer number (10154875).

Almost surely, 2^20309749 is an apocalyptic number.

It is an amenable number.

20309749 is a deficient number, since it is larger than the sum of its proper divisors (1).

20309749 is an equidigital number, since it uses as much as digits as its factorization.

20309749 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 13608, while the sum is 34.

The square root of 20309749 is about 4506.6338879479. The cubic root of 20309749 is about 272.8359025812.

The spelling of 20309749 in words is "twenty million, three hundred nine thousand, seven hundred forty-nine".