21534203993 has 2 divisors, whose sum is σ = 21534203994. Its totient is φ = 21534203992.

The previous prime is 21534203987. The next prime is 21534204053. The reversal of 21534203993 is 39930243512.

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., 18897176089 + 2637027904 = 137467^2 + 51352^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21534203993 is a prime.

It is a super-2 number, since 2×21534203993² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21534203993.

It is not a weakly prime, because it can be changed into another prime (21534203293) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10767101996 + 10767101997.

It is an arithmetic number, because the mean of its divisors is an integer number (10767101997).

Almost surely, 2^21534203993 is an apocalyptic number.

It is an amenable number.

21534203993 is a deficient number, since it is larger than the sum of its proper divisors (1).

21534203993 is an equidigital number, since it uses as much as digits as its factorization.

21534203993 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 174960, while the sum is 41.

The spelling of 21534203993 in words is "twenty-one billion, five hundred thirty-four million, two hundred three thousand, nine hundred ninety-three".