21736240 has 20 divisors (see below), whose sum is σ = 50536944. Its totient is φ = 8694464.

The previous prime is 21736237. The next prime is 21736259. The reversal of 21736240 is 4263712.

It is a tau number, because it is divible by the number of its divisors (20).

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 135772 + ... + 135931.

Almost surely, 2^21736240 is an apocalyptic number.

21736240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21736240 is an abundant number, since it is smaller than the sum of its proper divisors (28800704).

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

21736240 is a wasteful number, since it uses less digits than its factorization.

21736240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 271716 (or 271710 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 25.

The square root of 21736240 is about 4662.2140662994. The cubic root of 21736240 is about 279.0796310941.

Adding to 21736240 its reverse (4263712), we get a palindrome (25999952).

The spelling of 21736240 in words is "twenty-one million, seven hundred thirty-six thousand, two hundred forty".