21101405 has 8 divisors (see below), whose sum is σ = 27269592. Its totient is φ = 15582528.

The previous prime is 21101401. The next prime is 21101407. The reversal of 21101405 is 50410112.

It can be written as a sum of positive squares in 4 ways, for example, as 326041 + 20775364 = 571^2 + 4558^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21101405 - 2² = 21101401 is a prime.

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 21101405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21101401) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 162254 + ... + 162383.

It is an arithmetic number, because the mean of its divisors is an integer number (3408699).

Almost surely, 2^21101405 is an apocalyptic number.

It is an amenable number.

21101405 is a deficient number, since it is larger than the sum of its proper divisors (6168187).

21101405 is a wasteful number, since it uses less digits than its factorization.

21101405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 324655.

The product of its (nonzero) digits is 40, while the sum is 14.

The square root of 21101405 is about 4593.6265629674. The cubic root of 21101405 is about 276.3357820725.

Adding to 21101405 its reverse (50410112), we get a palindrome (71511517).

The spelling of 21101405 in words is "twenty-one million, one hundred one thousand, four hundred five".