21405117 has 8 divisors (see below), whose sum is σ = 28705824. Its totient is φ = 14187248.

The previous prime is 21405113. The next prime is 21405121. The reversal of 21405117 is 71150412.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21405113) and next prime (21405121).

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

It is a cyclic number.

It is not a de Polignac number, because 21405117 - 2² = 21405113 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21405093 and 21405102.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21405113) 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, 20103 + ... + 21140.

It is an arithmetic number, because the mean of its divisors is an integer number (3588228).

Almost surely, 2^21405117 is an apocalyptic number.

It is an amenable number.

21405117 is a deficient number, since it is larger than the sum of its proper divisors (7300707).

21405117 is a wasteful number, since it uses less digits than its factorization.

21405117 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41419.

The product of its (nonzero) digits is 280, while the sum is 21.

The square root of 21405117 is about 4626.5664374350. The cubic root of 21405117 is about 277.6552365743.

Adding to 21405117 its reverse (71150412), we get a palindrome (92555529).

The spelling of 21405117 in words is "twenty-one million, four hundred five thousand, one hundred seventeen".