21091587 has 16 divisors (see below), whose sum is σ = 30823680. Its totient is φ = 12722400.

The previous prime is 21091573. The next prime is 21091601. The reversal of 21091587 is 78519012.

It is an interprime number because it is at equal distance from previous prime (21091573) and next prime (21091601).

It is not a de Polignac number, because 21091587 - 2⁴ = 21091571 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is not an unprimeable number, because it can be changed into a prime (21091547) 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, 6162 + ... + 8952.

It is an arithmetic number, because the mean of its divisors is an integer number (1926480).

Almost surely, 2^21091587 is an apocalyptic number.

21091587 is a deficient number, since it is larger than the sum of its proper divisors (9732093).

21091587 is a wasteful number, since it uses less digits than its factorization.

21091587 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3034.

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

The square root of 21091587 is about 4592.5577840676. The cubic root of 21091587 is about 276.2929178558.

The spelling of 21091587 in words is "twenty-one million, ninety-one thousand, five hundred eighty-seven".