20518123605649 has 2 divisors, whose sum is σ = 20518123605650. Its totient is φ = 20518123605648.

The previous prime is 20518123605533. The next prime is 20518123605653. The reversal of 20518123605649 is 94650632181502.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18406716993025 + 2111406612624 = 4290305^2 + 1453068^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20518123605649 is a prime.

It is a super-2 number, since 2×20518123605649² (a number of 27 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 20518123605596 and 20518123605605.

It is not a weakly prime, because it can be changed into another prime (20518123605349) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10259061802824 + 10259061802825.

It is an arithmetic number, because the mean of its divisors is an integer number (10259061802825).

Almost surely, 2^{20518123605649} is an apocalyptic number.

It is an amenable number.

20518123605649 is a deficient number, since it is larger than the sum of its proper divisors (1).

20518123605649 is an equidigital number, since it uses as much as digits as its factorization.

20518123605649 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3110400, while the sum is 52.

The spelling of 20518123605649 in words is "twenty trillion, five hundred eighteen billion, one hundred twenty-three million, six hundred five thousand, six hundred forty-nine".