108991021 has 2 divisors, whose sum is σ = 108991022. Its totient is φ = 108991020.

The previous prime is 108990991. The next prime is 108991031. The reversal of 108991021 is 120199801.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 86769225 + 22221796 = 9315^2 + 4714^2 .

It is an emirp because it is prime and its reverse (120199801) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 108991021 - 2⁵ = 108990989 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (108991031) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 54495510 + 54495511.

It is an arithmetic number, because the mean of its divisors is an integer number (54495511).

Almost surely, 2^108991021 is an apocalyptic number.

It is an amenable number.

108991021 is a deficient number, since it is larger than the sum of its proper divisors (1).

108991021 is an equidigital number, since it uses as much as digits as its factorization.

108991021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1296, while the sum is 31.

The square root of 108991021 is about 10439.8764839437. The cubic root of 108991021 is about 477.6725011098.

The spelling of 108991021 in words is "one hundred eight million, nine hundred ninety-one thousand, twenty-one".