21320191 has 12 divisors (see below), whose sum is σ = 22388184. Its totient is φ = 20300000.

The previous prime is 21320183. The next prime is 21320197. The reversal of 21320191 is 19102312.

It is not a de Polignac number, because 21320191 - 2³ = 21320183 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21320197) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 84816 + ... + 85066.

It is an arithmetic number, because the mean of its divisors is an integer number (1865682).

Almost surely, 2^21320191 is an apocalyptic number.

21320191 is a deficient number, since it is larger than the sum of its proper divisors (1067993).

21320191 is a wasteful number, since it uses less digits than its factorization.

21320191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 410 (or 381 counting only the distinct ones).

The product of its (nonzero) digits is 108, while the sum is 19.

The square root of 21320191 is about 4617.3792350207. The cubic root of 21320191 is about 277.2875456350.

The spelling of 21320191 in words is "twenty-one million, three hundred twenty thousand, one hundred ninety-one".