100721521 has 2 divisors, whose sum is σ = 100721522. Its totient is φ = 100721520.

The previous prime is 100721507. The next prime is 100721539. The reversal of 100721521 is 125127001.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 100721296 + 225 = 10036^2 + 15^2 .

It is a cyclic number.

It is not a de Polignac number, because 100721521 - 2¹³ = 100713329 is a prime.

It is not a weakly prime, because it can be changed into another prime (100721501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 50360760 + 50360761.

It is an arithmetic number, because the mean of its divisors is an integer number (50360761).

Almost surely, 2^100721521 is an apocalyptic number.

It is an amenable number.

100721521 is a deficient number, since it is larger than the sum of its proper divisors (1).

100721521 is an equidigital number, since it uses as much as digits as its factorization.

100721521 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 140, while the sum is 19.

The square root of 100721521 is about 10036.0112096390. The cubic root of 100721521 is about 465.2725438147.

Adding to 100721521 its reverse (125127001), we get a palindrome (225848522).

The spelling of 100721521 in words is "one hundred million, seven hundred twenty-one thousand, five hundred twenty-one".