21481944 has 32 divisors (see below), whose sum is σ = 58587840. Its totient is φ = 6509600.

The previous prime is 21481939. The next prime is 21481949. The reversal of 21481944 is 44918412.

It is an interprime number because it is at equal distance from previous prime (21481939) and next prime (21481949).

It is a super-2 number, since 2×21481944² = 922947836038272, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21481949) 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 7 ways as a sum of consecutive naturals, for example, 40422 + ... + 40949.

It is an arithmetic number, because the mean of its divisors is an integer number (1830870).

Almost surely, 2^21481944 is an apocalyptic number.

21481944 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21481944 is an abundant number, since it is smaller than the sum of its proper divisors (37105896).

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

21481944 is a wasteful number, since it uses less digits than its factorization.

21481944 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 81391 (or 81387 counting only the distinct ones).

The product of its digits is 9216, while the sum is 33.

The square root of 21481944 is about 4634.8618102377. The cubic root of 21481944 is about 277.9870256009.

The spelling of 21481944 in words is "twenty-one million, four hundred eighty-one thousand, nine hundred forty-four".