999420821619221 has 4 divisors (see below), whose sum is σ = 999420894627744. Its totient is φ = 999420748610700.

The previous prime is 999420821619169. The next prime is 999420821619239. The reversal of 999420821619221 is 122916128024999.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-999420821619221 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (999420821619821) 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, 9126065 + ... + 45630326.

It is an arithmetic number, because the mean of its divisors is an integer number (249855223656936).

It is a Poulet number, since it divides 2^{999420821619220}-1.

Almost surely, 2^{999420821619221} is an apocalyptic number.

999420821619221 is the 18252131-st octagonal number.

It is an amenable number.

999420821619221 is a deficient number, since it is larger than the sum of its proper divisors (73008523).

999420821619221 is a wasteful number, since it uses less digits than its factorization.

999420821619221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73008522.

The product of its (nonzero) digits is 20155392, while the sum is 65.

The spelling of 999420821619221 in words is "nine hundred ninety-nine trillion, four hundred twenty billion, eight hundred twenty-one million, six hundred nineteen thousand, two hundred twenty-one".