21281712816 has 80 divisors (see below), whose sum is σ = 67664946944. Its totient is φ = 5612758272.

The previous prime is 21281712811. The next prime is 21281712817. The reversal of 21281712816 is 61821718212.

It is a super-2 number, since 2×21281712816² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (21281712811) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2431726 + ... + 2440461.

Almost surely, 2^21281712816 is an apocalyptic number.

21281712816 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

21281712816 is an abundant number, since it is smaller than the sum of its proper divisors (46383234128).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21281712816 is a wasteful number, since it uses less digits than its factorization.

21281712816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4872218 (or 4872212 counting only the distinct ones).

The product of its digits is 21504, while the sum is 39.

The spelling of 21281712816 in words is "twenty-one billion, two hundred eighty-one million, seven hundred twelve thousand, eight hundred sixteen".