163121721 has 32 divisors (see below), whose sum is σ = 258736128. Its totient is φ = 89449920.

The previous prime is 163121711. The next prime is 163121729. The reversal of 163121721 is 127121361.

It is not a de Polignac number, because 163121721 - 2¹³ = 163113529 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 163121691 and 163121700.

It is not an unprimeable number, because it can be changed into a prime (163121729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 81691 + ... + 83663.

It is an arithmetic number, because the mean of its divisors is an integer number (8085504).

Almost surely, 2^163121721 is an apocalyptic number.

It is an amenable number.

163121721 is a deficient number, since it is larger than the sum of its proper divisors (95614407).

163121721 is a wasteful number, since it uses less digits than its factorization.

163121721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2141.

The product of its digits is 504, while the sum is 24.

The square root of 163121721 is about 12771.9114074597. The cubic root of 163121721 is about 546.3914962463.

The spelling of 163121721 in words is "one hundred sixty-three million, one hundred twenty-one thousand, seven hundred twenty-one".