163788991021 has 2 divisors, whose sum is σ = 163788991022. Its totient is φ = 163788991020.

The previous prime is 163788991007. The next prime is 163788991141. The reversal of 163788991021 is 120199887361.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 160271314921 + 3517676100 = 400339^2 + 59310^2 .

It is a cyclic number.

It is not a de Polignac number, because 163788991021 - 2²¹ = 163786893869 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (163788911021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 81894495510 + 81894495511.

It is an arithmetic number, because the mean of its divisors is an integer number (81894495511).

Almost surely, 2^163788991021 is an apocalyptic number.

It is an amenable number.

163788991021 is a deficient number, since it is larger than the sum of its proper divisors (1).

163788991021 is an equidigital number, since it uses as much as digits as its factorization.

163788991021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1306368, while the sum is 55.

The spelling of 163788991021 in words is "one hundred sixty-three billion, seven hundred eighty-eight million, nine hundred ninety-one thousand, twenty-one".