21430297981 has 2 divisors, whose sum is σ = 21430297982. Its totient is φ = 21430297980.

The previous prime is 21430297949. The next prime is 21430298003. The reversal of 21430297981 is 18979203412.

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., 20042064900 + 1388233081 = 141570^2 + 37259^2 .

It is a cyclic number.

It is not a de Polignac number, because 21430297981 - 2⁵ = 21430297949 is a prime.

It is a super-2 number, since 2×21430297981² (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 (21430297181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10715148990 + 10715148991.

It is an arithmetic number, because the mean of its divisors is an integer number (10715148991).

Almost surely, 2^21430297981 is an apocalyptic number.

It is an amenable number.

21430297981 is a deficient number, since it is larger than the sum of its proper divisors (1).

21430297981 is an equidigital number, since it uses as much as digits as its factorization.

21430297981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 217728, while the sum is 46.

The spelling of 21430297981 in words is "twenty-one billion, four hundred thirty million, two hundred ninety-seven thousand, nine hundred eighty-one".