21037709 has 24 divisors (see below), whose sum is σ = 27874368. Its totient is φ = 15671040.

The previous prime is 21037703. The next prime is 21037727. The reversal of 21037709 is 90773012.

It is a happy number.

It is not a de Polignac number, because 21037709 - 2¹⁶ = 20972173 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 (21037703) 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, 11549 + ... + 13245.

It is an arithmetic number, because the mean of its divisors is an integer number (1161432).

Almost surely, 2^21037709 is an apocalyptic number.

It is an amenable number.

21037709 is a deficient number, since it is larger than the sum of its proper divisors (6836659).

21037709 is a wasteful number, since it uses less digits than its factorization.

21037709 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1745 (or 1738 counting only the distinct ones).

The product of its (nonzero) digits is 2646, while the sum is 29.

The square root of 21037709 is about 4586.6882388059. The cubic root of 21037709 is about 276.0574558323.

The spelling of 21037709 in words is "twenty-one million, thirty-seven thousand, seven hundred nine".