21743240 has 32 divisors (see below), whose sum is σ = 49097880. Its totient is φ = 8666112.

The previous prime is 21743213. The next prime is 21743263. The reversal of 21743240 is 4234712.

It can be written as a sum of positive squares in 4 ways, for example, as 16370116 + 5373124 = 4046^2 + 2318^2 .

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, 12674 + ... + 14286.

Almost surely, 2^21743240 is an apocalyptic number.

21743240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21743240 is an abundant number, since it is smaller than the sum of its proper divisors (27354640).

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

21743240 is a wasteful number, since it uses less digits than its factorization.

21743240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1961 (or 1957 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 23.

The square root of 21743240 is about 4662.9647221483. The cubic root of 21743240 is about 279.1095864090.

Adding to 21743240 its reverse (4234712), we get a palindrome (25977952).

The spelling of 21743240 in words is "twenty-one million, seven hundred forty-three thousand, two hundred forty".