21057161 has 4 divisors (see below), whose sum is σ = 21783300. Its totient is φ = 20331024.

The previous prime is 21057151. The next prime is 21057173. The reversal of 21057161 is 16175012.

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 8497225 + 12559936 = 2915^2 + 3544^2 .

It is a cyclic number.

It is not a de Polignac number, because 21057161 - 2¹⁴ = 21040777 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21057131) 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, 363026 + ... + 363083.

It is an arithmetic number, because the mean of its divisors is an integer number (5445825).

Almost surely, 2^21057161 is an apocalyptic number.

It is an amenable number.

21057161 is a deficient number, since it is larger than the sum of its proper divisors (726139).

21057161 is an equidigital number, since it uses as much as digits as its factorization.

21057161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 726138.

The product of its (nonzero) digits is 420, while the sum is 23.

The square root of 21057161 is about 4588.8082330819. The cubic root of 21057161 is about 276.1425128671.

The spelling of 21057161 in words is "twenty-one million, fifty-seven thousand, one hundred sixty-one".