21749440 has 28 divisors (see below), whose sum is σ = 51791616. Its totient is φ = 8699648.

The previous prime is 21749423. The next prime is 21749447. The reversal of 21749440 is 4494712.

It is not an unprimeable number, because it can be changed into a prime (21749447) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 33664 + ... + 34303.

Almost surely, 2^21749440 is an apocalyptic number.

21749440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21749440 is an abundant number, since it is smaller than the sum of its proper divisors (30042176).

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

21749440 is an equidigital number, since it uses as much as digits as its factorization.

21749440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67984 (or 67974 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 31.

The square root of 21749440 is about 4663.6294878560. The cubic root of 21749440 is about 279.1361128909.

The spelling of 21749440 in words is "twenty-one million, seven hundred forty-nine thousand, four hundred forty".