20999761564697 has 4 divisors (see below), whose sum is σ = 22235041656756. Its totient is φ = 19764481472640.

The previous prime is 20999761564681. The next prime is 20999761564723. The reversal of 20999761564697 is 79646516799902.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 17976489137161 + 3023272427536 = 4239869^2 + 1738756^2 .

It is a cyclic number.

It is not a de Polignac number, because 20999761564697 - 2⁴ = 20999761564681 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20999761564657) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 617640046004 + ... + 617640046037.

It is an arithmetic number, because the mean of its divisors is an integer number (5558760414189).

Almost surely, 2^{20999761564697} is an apocalyptic number.

It is an amenable number.

20999761564697 is a deficient number, since it is larger than the sum of its proper divisors (1235280092059).

20999761564697 is a wasteful number, since it uses less digits than its factorization.

20999761564697 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1235280092058.

The product of its (nonzero) digits is 2777664960, while the sum is 80.

The spelling of 20999761564697 in words is "twenty trillion, nine hundred ninety-nine billion, seven hundred sixty-one million, five hundred sixty-four thousand, six hundred ninety-seven".