21749740 has 12 divisors (see below), whose sum is σ = 45674496. Its totient is φ = 8699888.

The previous prime is 21749729. The next prime is 21749759. The reversal of 21749740 is 4794712.

It is a junction number, because it is equal to n+sod(n) for n = 21749696 and 21749705.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 543724 + ... + 543763.

It is an arithmetic number, because the mean of its divisors is an integer number (3806208).

Almost surely, 2^21749740 is an apocalyptic number.

21749740 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21749740 is an abundant number, since it is smaller than the sum of its proper divisors (23924756).

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

21749740 is a wasteful number, since it uses less digits than its factorization.

21749740 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1087496 (or 1087494 counting only the distinct ones).

The product of its (nonzero) digits is 14112, while the sum is 34.

The square root of 21749740 is about 4663.6616515352. The cubic root of 21749740 is about 279.1373963024.

The spelling of 21749740 in words is "twenty-one million, seven hundred forty-nine thousand, seven hundred forty".