21493162081 has 4 divisors (see below), whose sum is σ = 21507676164. Its totient is φ = 21478648000.

The previous prime is 21493162069. The next prime is 21493162091. The reversal of 21493162081 is 18026139412.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8085606400 + 13407555681 = 89920^2 + 115791^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21493162081 is a prime.

It is a super-2 number, since 2×21493162081² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21493162081.

It is not an unprimeable number, because it can be changed into a prime (21493162091) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7254820 + ... + 7257781.

It is an arithmetic number, because the mean of its divisors is an integer number (5376919041).

Almost surely, 2^21493162081 is an apocalyptic number.

It is an amenable number.

21493162081 is a deficient number, since it is larger than the sum of its proper divisors (14514083).

21493162081 is a wasteful number, since it uses less digits than its factorization.

21493162081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14514082.

The product of its (nonzero) digits is 20736, while the sum is 37.

The spelling of 21493162081 in words is "twenty-one billion, four hundred ninety-three million, one hundred sixty-two thousand, eighty-one".