21613280 has 48 divisors (see below), whose sum is σ = 54994464. Its totient is φ = 7979520.

The previous prime is 21613259. The next prime is 21613309. The reversal of 21613280 is 8231612.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3116 + ... + 7275.

It is an arithmetic number, because the mean of its divisors is an integer number (1145718).

Almost surely, 2^21613280 is an apocalyptic number.

21613280 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21613280 is an abundant number, since it is smaller than the sum of its proper divisors (33381184).

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

21613280 is a wasteful number, since it uses less digits than its factorization.

21613280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10419 (or 10411 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 21613280 is about 4649.0084964431. The cubic root of 21613280 is about 278.5523926756.

Adding to 21613280 its reverse (8231612), we get a palindrome (29844892).

The spelling of 21613280 in words is "twenty-one million, six hundred thirteen thousand, two hundred eighty".