491020021 has 4 divisors (see below), whose sum is σ = 516863200. Its totient is φ = 465176844.

The previous prime is 491020009. The next prime is 491020063. The reversal of 491020021 is 120020194.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 491020021 - 2¹⁵ = 490987253 is a prime.

It is a super-2 number, since 2×491020021² = 482201322045680882, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (19), and also a Moran number because the ratio is a prime number: 25843159 = 491020021 / (4 + 9 + 1 + 0 + 2 + 0 + 0 + 2 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (491020001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12921561 + ... + 12921598.

It is an arithmetic number, because the mean of its divisors is an integer number (129215800).

Almost surely, 2^491020021 is an apocalyptic number.

It is an amenable number.

491020021 is a deficient number, since it is larger than the sum of its proper divisors (25843179).

491020021 is a wasteful number, since it uses less digits than its factorization.

491020021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25843178.

The product of its (nonzero) digits is 144, while the sum is 19.

The square root of 491020021 is about 22158.9715690959. The cubic root of 491020021 is about 788.9201831055.

The spelling of 491020021 in words is "four hundred ninety-one million, twenty thousand, twenty-one".