99721521 has 6 divisors (see below), whose sum is σ = 144042210. Its totient is φ = 66481008.

The previous prime is 99721511. The next prime is 99721579. The reversal of 99721521 is 12512799.

It can be written as a sum of positive squares in only one way, i.e., 51279921 + 48441600 = 7161^2 + 6960^2 .

It is not a de Polignac number, because 99721521 - 2⁹ = 99721009 is a prime.

It is not an unprimeable number, because it can be changed into a prime (99721511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 5540076 + ... + 5540093.

It is an arithmetic number, because the mean of its divisors is an integer number (24007035).

Almost surely, 2^99721521 is an apocalyptic number.

It is an amenable number.

99721521 is a deficient number, since it is larger than the sum of its proper divisors (44320689).

99721521 is a wasteful number, since it uses less digits than its factorization.

99721521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11080175 (or 11080172 counting only the distinct ones).

The product of its digits is 11340, while the sum is 36.

The square root of 99721521 is about 9986.0663426597. The cubic root of 99721521 is about 463.7276211160.

The spelling of 99721521 in words is "ninety-nine million, seven hundred twenty-one thousand, five hundred twenty-one".