20491359281 has 4 divisors (see below), whose sum is σ = 20491645812. Its totient is φ = 20491072752.

The previous prime is 20491359253. The next prime is 20491359299. The reversal of 20491359281 is 18295319402.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 18295319402 = 2 ⋅9147659701.

It can be written as a sum of positive squares in 2 ways, for example, as 5366295025 + 15125064256 = 73255^2 + 122984^2 .

It is a cyclic number.

It is not a de Polignac number, because 20491359281 - 2¹⁴ = 20491342897 is a prime.

It is a super-2 number, since 2×20491359281² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20491359881) 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, 62951 + ... + 212003.

It is an arithmetic number, because the mean of its divisors is an integer number (5122911453).

Almost surely, 2^20491359281 is an apocalyptic number.

It is an amenable number.

20491359281 is a deficient number, since it is larger than the sum of its proper divisors (286531).

20491359281 is a wasteful number, since it uses less digits than its factorization.

20491359281 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 286530.

The product of its (nonzero) digits is 155520, while the sum is 44.

The spelling of 20491359281 in words is "twenty billion, four hundred ninety-one million, three hundred fifty-nine thousand, two hundred eighty-one".