21587091 has 4 divisors (see below), whose sum is σ = 28782792. Its totient is φ = 14391392.

The previous prime is 21587089. The next prime is 21587101. The reversal of 21587091 is 19078512.

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 21587091 - 2¹ = 21587089 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21587081) 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, 3597846 + ... + 3597851.

It is an arithmetic number, because the mean of its divisors is an integer number (7195698).

Almost surely, 2^21587091 is an apocalyptic number.

21587091 is a deficient number, since it is larger than the sum of its proper divisors (7195701).

21587091 is an equidigital number, since it uses as much as digits as its factorization.

21587091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7195700.

The product of its (nonzero) digits is 5040, while the sum is 33.

The square root of 21587091 is about 4646.1910206103. The cubic root of 21587091 is about 278.4398390809.

The spelling of 21587091 in words is "twenty-one million, five hundred eighty-seven thousand, ninety-one".