163871945721 has 189 divisors, whose sum is σ = 285773212543. Its totient is φ = 93851382240.

The previous prime is 163871945719. The next prime is 163871945749. The reversal of 163871945721 is 127549178361.

The square root of 163871945721 is 404811.

It is a perfect power (a square), and thus also a powerful number.

163871945721 is a `hidden beast` number, since 1 + 6 + 387 + 194 + 5 + 72 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 85930473321 + 77941472400 = 293139^2 + 279180^2 .

It is not a de Polignac number, because 163871945721 - 2¹ = 163871945719 is a prime.

It is a Duffinian number.

Its product of digits (2540160) is a multiple of the sum of its prime divisors (90).

It is not an unprimeable number, because it can be changed into a prime (163871945701) by changing a digit.

It is a polite number, since it can be written in 188 ways as a sum of consecutive naturals, for example, 3486637120 + ... + 3486637166.

Almost surely, 2^163871945721 is an apocalyptic number.

163871945721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

163871945721 is the 404811-st square number.

163871945721 is the 202406-th centered octagonal number.

It is an amenable number.

163871945721 is a deficient number, since it is larger than the sum of its proper divisors (121901266822).

163871945721 is an frugal number, since it uses more digits than its factorization.

163871945721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 192 (or 90 counting only the distinct ones).

The product of its digits is 2540160, while the sum is 54.

The spelling of 163871945721 in words is "one hundred sixty-three billion, eight hundred seventy-one million, nine hundred forty-five thousand, seven hundred twenty-one".