21066637 has 4 divisors (see below), whose sum is σ = 21081340. Its totient is φ = 21051936.

The previous prime is 21066613. The next prime is 21066641. The reversal of 21066637 is 73666012.

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 19945156 + 1121481 = 4466^2 + 1059^2 .

It is a cyclic number.

It is not a de Polignac number, because 21066637 - 2⁷ = 21066509 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21066599 and 21066608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21066607) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4938 + ... + 8155.

It is an arithmetic number, because the mean of its divisors is an integer number (5270335).

Almost surely, 2^21066637 is an apocalyptic number.

It is an amenable number.

21066637 is a deficient number, since it is larger than the sum of its proper divisors (14703).

21066637 is a wasteful number, since it uses less digits than its factorization.

21066637 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14702.

The product of its (nonzero) digits is 9072, while the sum is 31.

The square root of 21066637 is about 4589.8406290415. The cubic root of 21066637 is about 276.1839292453.

The spelling of 21066637 in words is "twenty-one million, sixty-six thousand, six hundred thirty-seven".