21415688281 has 9 divisors (see below), whose sum is σ = 23191829181. Its totient is φ = 19766571552.

The previous prime is 21415688251. The next prime is 21415688293. The reversal of 21415688281 is 18288651412.

It is a happy number.

The square root of 21415688281 is 146341.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 292681 + 21415395600 = 541^2 + 146340^2 .

It is not a de Polignac number, because 21415688281 - 2³¹ = 19268204633 is a prime.

It is a super-2 number, since 2×21415688281² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21415688221) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 1896805 + ... + 1908061.

It is an arithmetic number, because the mean of its divisors is an integer number (2576869909).

Almost surely, 2^21415688281 is an apocalyptic number.

21415688281 is the 146341-st square number.

21415688281 is the 73171-st centered octagonal number.

It is an amenable number.

21415688281 is a deficient number, since it is larger than the sum of its proper divisors (1776140900).

21415688281 is an frugal number, since it uses more digits than its factorization.

21415688281 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22540 (or 11270 counting only the distinct ones).

The product of its digits is 245760, while the sum is 46.

The spelling of 21415688281 in words is "twenty-one billion, four hundred fifteen million, six hundred eighty-eight thousand, two hundred eighty-one".