99178721 has 4 divisors (see below), whose sum is σ = 99844500. Its totient is φ = 98512944.

The previous prime is 99178711. The next prime is 99178747. The reversal of 99178721 is 12787199.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12787199 = 839 ⋅15241.

It can be written as a sum of positive squares in 2 ways, for example, as 4389025 + 94789696 = 2095^2 + 9736^2 .

It is a cyclic number.

It is not a de Polignac number, because 99178721 - 2¹⁴ = 99162337 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (99178711) 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, 332666 + ... + 332963.

It is an arithmetic number, because the mean of its divisors is an integer number (24961125).

Almost surely, 2^99178721 is an apocalyptic number.

It is an amenable number.

99178721 is a deficient number, since it is larger than the sum of its proper divisors (665779).

99178721 is a wasteful number, since it uses less digits than its factorization.

99178721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 665778.

The product of its digits is 63504, while the sum is 44.

The square root of 99178721 is about 9958.8513895931. The cubic root of 99178721 is about 462.8847089814.

It can be divided in two parts, 99178 and 721, that added together give a palindrome (99899).

The spelling of 99178721 in words is "ninety-nine million, one hundred seventy-eight thousand, seven hundred twenty-one".