21101705 has 16 divisors (see below), whose sum is σ = 26341200. Its totient is φ = 16208640.

The previous prime is 21101701. The next prime is 21101737. The reversal of 21101705 is 50710112.

It can be written as a sum of positive squares in 8 ways, for example, as 2808976 + 18292729 = 1676^2 + 4277^2 .

It is not a de Polignac number, because 21101705 - 2² = 21101701 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21101701) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 38735 + ... + 39275.

It is an arithmetic number, because the mean of its divisors is an integer number (1646325).

Almost surely, 2^21101705 is an apocalyptic number.

It is an amenable number.

21101705 is a deficient number, since it is larger than the sum of its proper divisors (5239495).

21101705 is a wasteful number, since it uses less digits than its factorization.

21101705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 844.

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

The square root of 21101705 is about 4593.6592167900. The cubic root of 21101705 is about 276.3370916274.

Adding to 21101705 its reverse (50710112), we get a palindrome (71811817).

The spelling of 21101705 in words is "twenty-one million, one hundred one thousand, seven hundred five".