21405518039 has 2 divisors, whose sum is σ = 21405518040. Its totient is φ = 21405518038.

The previous prime is 21405518021. The next prime is 21405518051. The reversal of 21405518039 is 93081550412.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21405518039 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21405517993 and 21405518011.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21405518339) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10702759019 + 10702759020.

It is an arithmetic number, because the mean of its divisors is an integer number (10702759020).

Almost surely, 2^21405518039 is an apocalyptic number.

21405518039 is a deficient number, since it is larger than the sum of its proper divisors (1).

21405518039 is an equidigital number, since it uses as much as digits as its factorization.

21405518039 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 43200, while the sum is 38.

The spelling of 21405518039 in words is "twenty-one billion, four hundred five million, five hundred eighteen thousand, thirty-nine".