20399636849 has 2 divisors, whose sum is σ = 20399636850. Its totient is φ = 20399636848.

The previous prime is 20399636827. The next prime is 20399636909. The reversal of 20399636849 is 94863699302.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18764890225 + 1634746624 = 136985^2 + 40432^2 .

It is a cyclic number.

It is not a de Polignac number, because 20399636849 - 2¹² = 20399632753 is a prime.

It is a super-2 number, since 2×20399636849² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (20399636449) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10199818424 + 10199818425.

It is an arithmetic number, because the mean of its divisors is an integer number (10199818425).

Almost surely, 2^20399636849 is an apocalyptic number.

It is an amenable number.

20399636849 is a deficient number, since it is larger than the sum of its proper divisors (1).

20399636849 is an equidigital number, since it uses as much as digits as its factorization.

20399636849 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 15116544, while the sum is 59.

The spelling of 20399636849 in words is "twenty billion, three hundred ninety-nine million, six hundred thirty-six thousand, eight hundred forty-nine".