21240747 has 24 divisors (see below), whose sum is σ = 34293168. Its totient is φ = 12556800.

The previous prime is 21240743. The next prime is 21240761. The reversal of 21240747 is 74704212.

It is a happy number.

21240747 is a `hidden beast` number, since 212 + 407 + 47 = 666.

It is not a de Polignac number, because 21240747 - 2² = 21240743 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21240747.

It is not an unprimeable number, because it can be changed into a prime (21240743) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1443 + ... + 6675.

It is an arithmetic number, because the mean of its divisors is an integer number (1428882).

Almost surely, 2^21240747 is an apocalyptic number.

21240747 is a deficient number, since it is larger than the sum of its proper divisors (13052421).

21240747 is a wasteful number, since it uses less digits than its factorization.

21240747 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5291 (or 5288 counting only the distinct ones).

The product of its (nonzero) digits is 3136, while the sum is 27.

The square root of 21240747 is about 4608.7684906057. The cubic root of 21240747 is about 276.9427042890.

Adding to 21240747 its reverse (74704212), we get a palindrome (95944959).

The spelling of 21240747 in words is "twenty-one million, two hundred forty thousand, seven hundred forty-seven".