21801972277 has 2 divisors, whose sum is σ = 21801972278. Its totient is φ = 21801972276.

The previous prime is 21801972223. The next prime is 21801972281. The reversal of 21801972277 is 77227910812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17089287076 + 4712685201 = 130726^2 + 68649^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21801972277 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21801972217) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10900986138 + 10900986139.

It is an arithmetic number, because the mean of its divisors is an integer number (10900986139).

Almost surely, 2^21801972277 is an apocalyptic number.

It is an amenable number.

21801972277 is a deficient number, since it is larger than the sum of its proper divisors (1).

21801972277 is an equidigital number, since it uses as much as digits as its factorization.

21801972277 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 197568, while the sum is 46.

The spelling of 21801972277 in words is "twenty-one billion, eight hundred one million, nine hundred seventy-two thousand, two hundred seventy-seven".