191091021 has 16 divisors (see below), whose sum is σ = 278208000. Its totient is φ = 115705520.

The previous prime is 191091013. The next prime is 191091031. The reversal of 191091021 is 120190191.

It is a cyclic number.

It is not a de Polignac number, because 191091021 - 2³ = 191091013 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 191090982 and 191091000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (191091001) 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, 47536 + ... + 51398.

It is an arithmetic number, because the mean of its divisors is an integer number (17388000).

Almost surely, 2^191091021 is an apocalyptic number.

191091021 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

191091021 is a deficient number, since it is larger than the sum of its proper divisors (87116979).

191091021 is a wasteful number, since it uses less digits than its factorization.

191091021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5376.

The product of its (nonzero) digits is 162, while the sum is 24.

The square root of 191091021 is about 13823.5675930637. The cubic root of 191091021 is about 575.9879886336.

The spelling of 191091021 in words is "one hundred ninety-one million, ninety-one thousand, twenty-one".