21432144401981 has 2 divisors, whose sum is σ = 21432144401982. Its totient is φ = 21432144401980.

The previous prime is 21432144401971. The next prime is 21432144402041. The reversal of 21432144401981 is 18910444123412.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11484365321881 + 9947779080100 = 3388859^2 + 3154010^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21432144401981 is a prime.

It is a super-2 number, since 2×21432144401981² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21432144401971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10716072200990 + 10716072200991.

It is an arithmetic number, because the mean of its divisors is an integer number (10716072200991).

Almost surely, 2^{21432144401981} is an apocalyptic number.

It is an amenable number.

21432144401981 is a deficient number, since it is larger than the sum of its proper divisors (1).

21432144401981 is an equidigital number, since it uses as much as digits as its factorization.

21432144401981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 221184, while the sum is 44.

The spelling of 21432144401981 in words is "twenty-one trillion, four hundred thirty-two billion, one hundred forty-four million, four hundred one thousand, nine hundred eighty-one".