21705101 has 6 divisors (see below), whose sum is σ = 23857806. Its totient is φ = 19731800.

The previous prime is 21705091. The next prime is 21705133. The reversal of 21705101 is 10150712.

It can be written as a sum of positive squares in only one way, i.e., 20241001 + 1464100 = 4499^2 + 1210^2 .

It is not a de Polignac number, because 21705101 - 2¹⁰ = 21704077 is a prime.

It is a super-2 number, since 2×21705101² = 942222818840402, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21705101.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21705161) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 89570 + ... + 89811.

It is an arithmetic number, because the mean of its divisors is an integer number (3976301).

Almost surely, 2^21705101 is an apocalyptic number.

It is an amenable number.

21705101 is a deficient number, since it is larger than the sum of its proper divisors (2152705).

21705101 is a wasteful number, since it uses less digits than its factorization.

21705101 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 179403 (or 179392 counting only the distinct ones).

The product of its (nonzero) digits is 70, while the sum is 17.

The square root of 21705101 is about 4658.8733616616. The cubic root of 21705101 is about 278.9462990216.

Adding to 21705101 its reverse (10150712), we get a palindrome (31855813).

The spelling of 21705101 in words is "twenty-one million, seven hundred five thousand, one hundred one".