21247637 has 4 divisors (see below), whose sum is σ = 22497516. Its totient is φ = 19997760.

The previous prime is 21247631. The next prime is 21247649. The reversal of 21247637 is 73674212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8814961 + 12432676 = 2969^2 + 3526^2 .

It is a cyclic number.

It is not a de Polignac number, because 21247637 - 2⁴ = 21247621 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21247631) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 624914 + ... + 624947.

It is an arithmetic number, because the mean of its divisors is an integer number (5624379).

Almost surely, 2^21247637 is an apocalyptic number.

It is an amenable number.

21247637 is a deficient number, since it is larger than the sum of its proper divisors (1249879).

21247637 is a wasteful number, since it uses less digits than its factorization.

21247637 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1249878.

The product of its digits is 14112, while the sum is 32.

The square root of 21247637 is about 4609.5159181849. The cubic root of 21247637 is about 276.9726456238.

The spelling of 21247637 in words is "twenty-one million, two hundred forty-seven thousand, six hundred thirty-seven".