21008091 has 16 divisors (see below), whose sum is σ = 31754240. Its totient is φ = 12247200.

The previous prime is 21008083. The next prime is 21008149. The reversal of 21008091 is 19080012.

It is not a de Polignac number, because 21008091 - 2³ = 21008083 is a prime.

It is a super-3 number, since 3×21008091³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21008011) 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, 13435 + ... + 14916.

It is an arithmetic number, because the mean of its divisors is an integer number (1984640).

Almost surely, 2^21008091 is an apocalyptic number.

21008091 is a deficient number, since it is larger than the sum of its proper divisors (10746149).

21008091 is a wasteful number, since it uses less digits than its factorization.

21008091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28386.

The product of its (nonzero) digits is 144, while the sum is 21.

The square root of 21008091 is about 4583.4584104146. The cubic root of 21008091 is about 275.9278455576.

The spelling of 21008091 in words is "twenty-one million, eight thousand, ninety-one".