100721 has 4 divisors (see below), whose sum is σ = 102912. Its totient is φ = 98532.

The previous prime is 100703. The next prime is 100733. The reversal of 100721 is 127001.

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 an emirpimes, since its reverse is a distinct semiprime: 127001 = 7 ⋅18143.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-100721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (100741) 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, 1025 + ... + 1118.

It is an arithmetic number, because the mean of its divisors is an integer number (25728).

2¹⁰⁰⁷²¹ is an apocalyptic number.

It is an amenable number.

100721 is a deficient number, since it is larger than the sum of its proper divisors (2191).

100721 is an equidigital number, since it uses as much as digits as its factorization.

100721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2190.

The product of its (nonzero) digits is 14, while the sum is 11.

The square root of 100721 is about 317.3657196359. The cubic root of 100721 is about 46.5271741578.

Adding to 100721 its reverse (127001), we get a palindrome (227722).

The spelling of 100721 in words is "one hundred thousand, seven hundred twenty-one", and thus it is an iban number.