21280633 has 6 divisors (see below), whose sum is σ = 23391242. Its totient is φ = 19345920.

The previous prime is 21280579. The next prime is 21280639. The reversal of 21280633 is 33608212.

It can be written as a sum of positive squares in only one way, i.e., 20142144 + 1138489 = 4488^2 + 1067^2 .

It is not a de Polignac number, because 21280633 - 2¹³ = 21272441 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21280598 and 21280607.

It is not an unprimeable number, because it can be changed into a prime (21280639) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 87816 + ... + 88057.

Almost surely, 2^21280633 is an apocalyptic number.

It is an amenable number.

21280633 is a deficient number, since it is larger than the sum of its proper divisors (2110609).

21280633 is a wasteful number, since it uses less digits than its factorization.

21280633 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 175895 (or 175884 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 25.

The square root of 21280633 is about 4613.0936474344. The cubic root of 21280633 is about 277.1159441119.

Adding to 21280633 its reverse (33608212), we get a palindrome (54888845).

The spelling of 21280633 in words is "twenty-one million, two hundred eighty thousand, six hundred thirty-three".