21928129981 has 2 divisors, whose sum is σ = 21928129982. Its totient is φ = 21928129980.

The previous prime is 21928129963. The next prime is 21928129997. The reversal of 21928129981 is 18992182912.

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., 19954105081 + 1974024900 = 141259^2 + 44430^2 .

It is a cyclic number.

It is not a de Polignac number, because 21928129981 - 2⁹ = 21928129469 is a prime.

It is a super-2 number, since 2×21928129981² (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 (21928129481) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10964064990 + 10964064991.

It is an arithmetic number, because the mean of its divisors is an integer number (10964064991).

Almost surely, 2^21928129981 is an apocalyptic number.

It is an amenable number.

21928129981 is a deficient number, since it is larger than the sum of its proper divisors (1).

21928129981 is an equidigital number, since it uses as much as digits as its factorization.

21928129981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 373248, while the sum is 52.

The spelling of 21928129981 in words is "twenty-one billion, nine hundred twenty-eight million, one hundred twenty-nine thousand, nine hundred eighty-one".