28439921663981 has 2 divisors, whose sum is σ = 28439921663982. Its totient is φ = 28439921663980.

The previous prime is 28439921663971. The next prime is 28439921664013. The reversal of 28439921663981 is 18936612993482.

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., 18560630322025 + 9879291341956 = 4308205^2 + 3143134^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28439921663981 is a prime.

It is a super-2 number, since 2×28439921663981² (a number of 28 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28439921663921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14219960831990 + 14219960831991.

It is an arithmetic number, because the mean of its divisors is an integer number (14219960831991).

Almost surely, 2^{28439921663981} is an apocalyptic number.

It is an amenable number.

28439921663981 is a deficient number, since it is larger than the sum of its proper divisors (1).

28439921663981 is an equidigital number, since it uses as much as digits as its factorization.

28439921663981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 241864704, while the sum is 71.

The spelling of 28439921663981 in words is "twenty-eight trillion, four hundred thirty-nine billion, nine hundred twenty-one million, six hundred sixty-three thousand, nine hundred eighty-one".