21603161 has 4 divisors (see below), whose sum is σ = 21825972. Its totient is φ = 21380352.

The previous prime is 21603143. The next prime is 21603167. The reversal of 21603161 is 16130612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 15452761 + 6150400 = 3931^2 + 2480^2 .

It is not a de Polignac number, because 21603161 - 2⁶ = 21603097 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21603167) 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, 111260 + ... + 111453.

It is an arithmetic number, because the mean of its divisors is an integer number (5456493).

Almost surely, 2^21603161 is an apocalyptic number.

It is an amenable number.

21603161 is a deficient number, since it is larger than the sum of its proper divisors (222811).

21603161 is an equidigital number, since it uses as much as digits as its factorization.

21603161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 222810.

The product of its (nonzero) digits is 216, while the sum is 20.

The square root of 21603161 is about 4647.9200724625. The cubic root of 21603161 is about 278.5089145970.

Adding to 21603161 its reverse (16130612), we get a palindrome (37733773).

The spelling of 21603161 in words is "twenty-one million, six hundred three thousand, one hundred sixty-one".