993851921 has 4 divisors (see below), whose sum is σ = 996008244. Its totient is φ = 991695600.

The previous prime is 993851897. The next prime is 993851923. The reversal of 993851921 is 129158399.

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 637057600 + 356794321 = 25240^2 + 18889^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-993851921 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (993851923) 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, 1077470 + ... + 1078391.

It is an arithmetic number, because the mean of its divisors is an integer number (249002061).

Almost surely, 2^993851921 is an apocalyptic number.

It is an amenable number.

993851921 is a deficient number, since it is larger than the sum of its proper divisors (2156323).

993851921 is a wasteful number, since it uses less digits than its factorization.

993851921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2156322.

The product of its digits is 174960, while the sum is 47.

The square root of 993851921 is about 31525.4170630620. The cubic root of 993851921 is about 997.9464260541.

The spelling of 993851921 in words is "nine hundred ninety-three million, eight hundred fifty-one thousand, nine hundred twenty-one".