21099744 has 48 divisors (see below), whose sum is σ = 61543440. Its totient is φ = 7032960.

The previous prime is 21099739. The next prime is 21099751. The reversal of 21099744 is 44799012.

It is a tau number, because it is divible by the number of its divisors (48).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 21099699 and 21099708.

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, 11347 + ... + 13074.

It is an arithmetic number, because the mean of its divisors is an integer number (1282155).

Almost surely, 2^21099744 is an apocalyptic number.

21099744 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21099744 is an abundant number, since it is smaller than the sum of its proper divisors (40443696).

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

21099744 is a wasteful number, since it uses less digits than its factorization.

21099744 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24440 (or 24426 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 21099744 is about 4593.4457654358. The cubic root of 21099744 is about 276.3285312792.

The spelling of 21099744 in words is "twenty-one million, ninety-nine thousand, seven hundred forty-four".