21202091 has 4 divisors (see below), whose sum is σ = 21500784. Its totient is φ = 20903400.

The previous prime is 21202079. The next prime is 21202121. The reversal of 21202091 is 19020212.

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 21202091 - 2¹⁰ = 21201067 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21202001) 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, 149240 + ... + 149381.

It is an arithmetic number, because the mean of its divisors is an integer number (5375196).

Almost surely, 2^21202091 is an apocalyptic number.

21202091 is a deficient number, since it is larger than the sum of its proper divisors (298693).

21202091 is an equidigital number, since it uses as much as digits as its factorization.

21202091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 298692.

The product of its (nonzero) digits is 72, while the sum is 17.

The square root of 21202091 is about 4604.5728357797. The cubic root of 21202091 is about 276.7745997483.

The spelling of 21202091 in words is "twenty-one million, two hundred two thousand, ninety-one".