20787757477649 has 2 divisors, whose sum is σ = 20787757477650. Its totient is φ = 20787757477648.

The previous prime is 20787757477601. The next prime is 20787757477651. The reversal of 20787757477649 is 94677475778702.

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., 20352441231424 + 435316246225 = 4511368^2 + 659785^2 .

It is a cyclic number.

It is not a de Polignac number, because 20787757477649 - 2²⁰ = 20787756429073 is a prime.

Together with 20787757477651, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20787757477679) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10393878738824 + 10393878738825.

It is an arithmetic number, because the mean of its divisors is an integer number (10393878738825).

Almost surely, 2^{20787757477649} is an apocalyptic number.

It is an amenable number.

20787757477649 is a deficient number, since it is larger than the sum of its proper divisors (1).

20787757477649 is an equidigital number, since it uses as much as digits as its factorization.

20787757477649 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8131898880, while the sum is 80.

The spelling of 20787757477649 in words is "twenty trillion, seven hundred eighty-seven billion, seven hundred fifty-seven million, four hundred seventy-seven thousand, six hundred forty-nine".