999764221 has 4 divisors (see below), whose sum is σ = 1000744444. Its totient is φ = 998784000.

The previous prime is 999764219. The next prime is 999764231. The reversal of 999764221 is 122467999.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 599564196 + 400200025 = 24486^2 + 20005^2 .

It is a 5-Lehmer number, since φ(999764221) divides (999764221-1)⁵.

It is a cyclic number.

It is not a de Polignac number, because 999764221 - 2¹ = 999764219 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (999764201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 488580 + ... + 490621.

It is an arithmetic number, because the mean of its divisors is an integer number (250186111).

Almost surely, 2^999764221 is an apocalyptic number.

It is an amenable number.

999764221 is a deficient number, since it is larger than the sum of its proper divisors (980223).

999764221 is a wasteful number, since it uses less digits than its factorization.

999764221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 980222.

The product of its digits is 489888, while the sum is 49.

The square root of 999764221 is about 31619.0483885901. The cubic root of 999764221 is about 999.9214008223.

The spelling of 999764221 in words is "nine hundred ninety-nine million, seven hundred sixty-four thousand, two hundred twenty-one".