90721 has 4 divisors (see below), whose sum is σ = 91332. Its totient is φ = 90112.
The previous prime is 90709. The next prime is 90731. The reversal of 90721 is 12709.
90721 is nontrivially palindromic in base 16.
It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 12709 = 71 ⋅179.
It can be written as a sum of positive squares in 2 ways, for example, as 69696 + 21025 = 264^2 + 145^2 .
It is a cyclic number.
It is not a de Polignac number, because 90721 - 213 = 82529 is a prime.
It is an alternating number because its digits alternate between odd and even.
It is a Duffinian number.
It is not an unprimeable number, because it can be changed into a prime (90731) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (7) of ones.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 81 + ... + 433.
It is an arithmetic number, because the mean of its divisors is an integer number (22833).
290721 is an apocalyptic number.
It is an amenable number.
90721 is a deficient number, since it is larger than the sum of its proper divisors (611).
90721 is a wasteful number, since it uses less digits than its factorization.
90721 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 610.
The product of its (nonzero) digits is 126, while the sum is 19.
The square root of 90721 is about 301.1992695874. The cubic root of 90721 is about 44.9333994213.
The spelling of 90721 in words is "ninety thousand, seven hundred twenty-one".
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