21035639 has 16 divisors (see below), whose sum is σ = 22923264. Its totient is φ = 19245600.

The previous prime is 21035633. The next prime is 21035687. The reversal of 21035639 is 93653012.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21035639 is a prime.

It is a Smith number, since the sum of its digits (29) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21035633) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 116129 + ... + 116309.

It is an arithmetic number, because the mean of its divisors is an integer number (1432704).

Almost surely, 2^21035639 is an apocalyptic number.

21035639 is a deficient number, since it is larger than the sum of its proper divisors (1887625).

21035639 is a wasteful number, since it uses less digits than its factorization.

21035639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 398.

The product of its (nonzero) digits is 4860, while the sum is 29.

The square root of 21035639 is about 4586.4625802463. The cubic root of 21035639 is about 276.0484013344.

The spelling of 21035639 in words is "twenty-one million, thirty-five thousand, six hundred thirty-nine".