821272191 has 4 divisors (see below), whose sum is σ = 1095029592. Its totient is φ = 547514792.

The previous prime is 821272147. The next prime is 821272213. The reversal of 821272191 is 191272128.

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 821272191 - 2¹⁹ = 820747903 is a prime.

It is a zygodrome in base 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821272121) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 136878696 + ... + 136878701.

It is an arithmetic number, because the mean of its divisors is an integer number (273757398).

Almost surely, 2^821272191 is an apocalyptic number.

821272191 is a deficient number, since it is larger than the sum of its proper divisors (273757401).

821272191 is a wasteful number, since it uses less digits than its factorization.

821272191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 273757400.

The product of its digits is 4032, while the sum is 33.

The square root of 821272191 is about 28657.8469358743. The cubic root of 821272191 is about 936.4739602772.

The spelling of 821272191 in words is "eight hundred twenty-one million, two hundred seventy-two thousand, one hundred ninety-one".