21040024081 has 2 divisors, whose sum is σ = 21040024082. Its totient is φ = 21040024080.

The previous prime is 21040024067. The next prime is 21040024097. The reversal of 21040024081 is 18042004012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20991373456 + 48650625 = 144884^2 + 6975^2 .

It is a cyclic number.

It is not a de Polignac number, because 21040024081 - 2²³ = 21031635473 is a prime.

It is a super-2 number, since 2×21040024081² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21040024021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10520012040 + 10520012041.

It is an arithmetic number, because the mean of its divisors is an integer number (10520012041).

Almost surely, 2^21040024081 is an apocalyptic number.

It is an amenable number.

21040024081 is a deficient number, since it is larger than the sum of its proper divisors (1).

21040024081 is an equidigital number, since it uses as much as digits as its factorization.

21040024081 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 512, while the sum is 22.

Adding to 21040024081 its reverse (18042004012), we get a palindrome (39082028093).

The spelling of 21040024081 in words is "twenty-one billion, forty million, twenty-four thousand, eighty-one".