21002747 has 2 divisors, whose sum is σ = 21002748. Its totient is φ = 21002746.

The previous prime is 21002743. The next prime is 21002753. The reversal of 21002747 is 74720012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21002747 - 2² = 21002743 is a prime.

It is a super-2 number, since 2×21002747² = 882230763092018, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21002743) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10501373 + 10501374.

It is an arithmetic number, because the mean of its divisors is an integer number (10501374).

Almost surely, 2^21002747 is an apocalyptic number.

21002747 is a deficient number, since it is larger than the sum of its proper divisors (1).

21002747 is an equidigital number, since it uses as much as digits as its factorization.

21002747 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 784, while the sum is 23.

The square root of 21002747 is about 4582.8754074271. The cubic root of 21002747 is about 275.9044468989.

Adding to 21002747 its reverse (74720012), we get a palindrome (95722759).

The spelling of 21002747 in words is "twenty-one million, two thousand, seven hundred forty-seven".