21389721499 has 2 divisors, whose sum is σ = 21389721500. Its totient is φ = 21389721498.

The previous prime is 21389721449. The next prime is 21389721533. The reversal of 21389721499 is 99412798312.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21389721499 - 2¹¹ = 21389719451 is a prime.

It is not a weakly prime, because it can be changed into another prime (21389721439) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10694860749 + 10694860750.

It is an arithmetic number, because the mean of its divisors is an integer number (10694860750).

Almost surely, 2^21389721499 is an apocalyptic number.

21389721499 is a deficient number, since it is larger than the sum of its proper divisors (1).

21389721499 is an equidigital number, since it uses as much as digits as its factorization.

21389721499 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1959552, while the sum is 55.

The spelling of 21389721499 in words is "twenty-one billion, three hundred eighty-nine million, seven hundred twenty-one thousand, four hundred ninety-nine".