21781104 has 40 divisors (see below), whose sum is σ = 56544000. Its totient is φ = 7224768.

The previous prime is 21781093. The next prime is 21781129. The reversal of 21781104 is 40118712.

It is a Harshad number since it is a multiple of its sum of digits (24).

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, 9897 + ... + 11895.

It is an arithmetic number, because the mean of its divisors is an integer number (1413600).

Almost surely, 2^21781104 is an apocalyptic number.

21781104 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21781104 is an abundant number, since it is smaller than the sum of its proper divisors (34762896).

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

21781104 is a wasteful number, since it uses less digits than its factorization.

21781104 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2237 (or 2231 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 24.

The square root of 21781104 is about 4667.0230340122. The cubic root of 21781104 is about 279.2715076432.

Adding to 21781104 its reverse (40118712), we get a palindrome (61899816).

The spelling of 21781104 in words is "twenty-one million, seven hundred eighty-one thousand, one hundred four".