20857676561 has 2 divisors, whose sum is σ = 20857676562. Its totient is φ = 20857676560.

The previous prime is 20857676537. The next prime is 20857676611. The reversal of 20857676561 is 16567675802.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19287932161 + 1569744400 = 138881^2 + 39620^2 .

It is a cyclic number.

It is not a de Polignac number, because 20857676561 - 2²² = 20853482257 is a prime.

It is not a weakly prime, because it can be changed into another prime (20857673561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10428838280 + 10428838281.

It is an arithmetic number, because the mean of its divisors is an integer number (10428838281).

Almost surely, 2^20857676561 is an apocalyptic number.

It is an amenable number.

20857676561 is a deficient number, since it is larger than the sum of its proper divisors (1).

20857676561 is an equidigital number, since it uses as much as digits as its factorization.

20857676561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4233600, while the sum is 53.

The spelling of 20857676561 in words is "twenty billion, eight hundred fifty-seven million, six hundred seventy-six thousand, five hundred sixty-one".