21278348641 has 27 divisors (see below), whose sum is σ = 23814163513. Its totient is φ = 18998239040.

The previous prime is 21278348573. The next prime is 21278348659. The reversal of 21278348641 is 14684387212.

The square root of 21278348641 is 145871.

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 10265945041 + 11012403600 = 101321^2 + 104940^2 .

It is not a de Polignac number, because 21278348641 - 2⁷ = 21278348513 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21278348591 and 21278348600.

It is not an unprimeable number, because it can be changed into a prime (21278348671) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 142807635 + ... + 142807783.

Almost surely, 2^21278348641 is an apocalyptic number.

21278348641 is the 145871-st square number.

21278348641 is the 72936-th centered octagonal number.

It is an amenable number.

21278348641 is a deficient number, since it is larger than the sum of its proper divisors (2535814872).

21278348641 is an frugal number, since it uses more digits than its factorization.

21278348641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 498 (or 249 counting only the distinct ones).

The product of its digits is 516096, while the sum is 46.

The spelling of 21278348641 in words is "twenty-one billion, two hundred seventy-eight million, three hundred forty-eight thousand, six hundred forty-one".