21772799981 has 2 divisors, whose sum is σ = 21772799982. Its totient is φ = 21772799980.

The previous prime is 21772799911. The next prime is 21772799989. The reversal of 21772799981 is 18999727712.

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., 20019703081 + 1753096900 = 141491^2 + 41870^2 .

It is a cyclic number.

It is not a de Polignac number, because 21772799981 - 2¹⁴ = 21772783597 is a prime.

It is a super-2 number, since 2×21772799981² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21772799989) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10886399990 + 10886399991.

It is an arithmetic number, because the mean of its divisors is an integer number (10886399991).

Almost surely, 2^21772799981 is an apocalyptic number.

It is an amenable number.

21772799981 is a deficient number, since it is larger than the sum of its proper divisors (1).

21772799981 is an equidigital number, since it uses as much as digits as its factorization.

21772799981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8001504, while the sum is 62.

The spelling of 21772799981 in words is "twenty-one billion, seven hundred seventy-two million, seven hundred ninety-nine thousand, nine hundred eighty-one".