163520021 has 4 divisors (see below), whose sum is σ = 186880032. Its totient is φ = 140160012.

The previous prime is 163520011. The next prime is 163520051. The reversal of 163520021 is 120025361.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 120025361 = 5099 ⋅23539.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-163520021 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 163519975 and 163520002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (163520011) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11679995 + ... + 11680008.

It is an arithmetic number, because the mean of its divisors is an integer number (46720008).

Almost surely, 2^163520021 is an apocalyptic number.

It is an amenable number.

163520021 is a deficient number, since it is larger than the sum of its proper divisors (23360011).

163520021 is an equidigital number, since it uses as much as digits as its factorization.

163520021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23360010.

The product of its (nonzero) digits is 360, while the sum is 20.

The square root of 163520021 is about 12787.4947116314. The cubic root of 163520021 is about 546.8358491744.

Adding to 163520021 its reverse (120025361), we get a palindrome (283545382).

The spelling of 163520021 in words is "one hundred sixty-three million, five hundred twenty thousand, twenty-one".