21447740 has 12 divisors (see below), whose sum is σ = 45040296. Its totient is φ = 8579088.

The previous prime is 21447719. The next prime is 21447743. The reversal of 21447740 is 4774412.

It is a super-2 number, since 2×21447740² = 920011102215200, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21447743) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 536174 + ... + 536213.

It is an arithmetic number, because the mean of its divisors is an integer number (3753358).

Almost surely, 2^21447740 is an apocalyptic number.

21447740 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21447740 is an abundant number, since it is smaller than the sum of its proper divisors (23592556).

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

21447740 is a wasteful number, since it uses less digits than its factorization.

21447740 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1072396 (or 1072394 counting only the distinct ones).

The product of its (nonzero) digits is 6272, while the sum is 29.

The square root of 21447740 is about 4631.1704783996. The cubic root of 21447740 is about 277.8394083102.

The spelling of 21447740 in words is "twenty-one million, four hundred forty-seven thousand, seven hundred forty".