21021091 has 8 divisors (see below), whose sum is σ = 25872224. Its totient is φ = 16632000.

The previous prime is 21021083. The next prime is 21021101. The reversal of 21021091 is 19012012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21021091 - 2³ = 21021083 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21021001) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 115410 + ... + 115591.

It is an arithmetic number, because the mean of its divisors is an integer number (3234028).

Almost surely, 2^21021091 is an apocalyptic number.

21021091 is a deficient number, since it is larger than the sum of its proper divisors (4851133).

21021091 is a wasteful number, since it uses less digits than its factorization.

21021091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 231021.

The product of its (nonzero) digits is 36, while the sum is 16.

The square root of 21021091 is about 4584.8763342101. The cubic root of 21021091 is about 275.9847493849.

The spelling of 21021091 in words is "twenty-one million, twenty-one thousand, ninety-one".