21787170061 has 2 divisors, whose sum is σ = 21787170062. Its totient is φ = 21787170060.

The previous prime is 21787170043. The next prime is 21787170073. The reversal of 21787170061 is 16007178712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21277765161 + 509404900 = 145869^2 + 22570^2 .

It is a cyclic number.

It is not a de Polignac number, because 21787170061 - 2²⁵ = 21753615629 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21787169996 and 21787170023.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21787150061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10893585030 + 10893585031.

It is an arithmetic number, because the mean of its divisors is an integer number (10893585031).

Almost surely, 2^21787170061 is an apocalyptic number.

It is an amenable number.

21787170061 is a deficient number, since it is larger than the sum of its proper divisors (1).

21787170061 is an equidigital number, since it uses as much as digits as its factorization.

21787170061 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 32928, while the sum is 40.

The spelling of 21787170061 in words is "twenty-one billion, seven hundred eighty-seven million, one hundred seventy thousand, sixty-one".