21240671 has 4 divisors (see below), whose sum is σ = 21250344. Its totient is φ = 21231000.

The previous prime is 21240643. The next prime is 21240683. The reversal of 21240671 is 17604212.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21240671 is a prime.

It is a super-2 number, since 2×21240671² = 902332209060482, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21240631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 221 + ... + 6521.

It is an arithmetic number, because the mean of its divisors is an integer number (5312586).

Almost surely, 2^21240671 is an apocalyptic number.

21240671 is a deficient number, since it is larger than the sum of its proper divisors (9673).

21240671 is an equidigital number, since it uses as much as digits as its factorization.

21240671 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9672.

The product of its (nonzero) digits is 672, while the sum is 23.

The square root of 21240671 is about 4608.7602454456. The cubic root of 21240671 is about 276.9423739857.

Adding to 21240671 its reverse (17604212), we get a palindrome (38844883).

The spelling of 21240671 in words is "twenty-one million, two hundred forty thousand, six hundred seventy-one".