21091039 has 4 divisors (see below), whose sum is σ = 21137056. Its totient is φ = 21045024.

The previous prime is 21091009. The next prime is 21091051. The reversal of 21091039 is 93019012.

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

It is a cyclic number.

It is not a de Polignac number, because 21091039 - 2¹³ = 21082847 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 (21091009) 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, 22314 + ... + 23239.

It is an arithmetic number, because the mean of its divisors is an integer number (5284264).

Almost surely, 2^21091039 is an apocalyptic number.

21091039 is a deficient number, since it is larger than the sum of its proper divisors (46017).

21091039 is an equidigital number, since it uses as much as digits as its factorization.

21091039 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 46016.

The product of its (nonzero) digits is 486, while the sum is 25.

The square root of 21091039 is about 4592.4981219376. The cubic root of 21091039 is about 276.2905249612.

The spelling of 21091039 in words is "twenty-one million, ninety-one thousand, thirty-nine".