21870117 has 6 divisors (see below), whose sum is σ = 31590182. Its totient is φ = 14580072.

The previous prime is 21870103. The next prime is 21870127. The reversal of 21870117 is 71107812.

It can be written as a sum of positive squares in only one way, i.e., 12173121 + 9696996 = 3489^2 + 3114^2 .

It is not a de Polignac number, because 21870117 - 2⁶ = 21870053 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21870127) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1214998 + ... + 1215015.

Almost surely, 2^21870117 is an apocalyptic number.

It is an amenable number.

21870117 is a deficient number, since it is larger than the sum of its proper divisors (9720065).

21870117 is a wasteful number, since it uses less digits than its factorization.

21870117 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2430019 (or 2430016 counting only the distinct ones).

The product of its (nonzero) digits is 784, while the sum is 27.

The square root of 21870117 is about 4676.5496896751. The cubic root of 21870117 is about 279.6514242266.

Adding to 21870117 its reverse (71107812), we get a palindrome (92977929).

The spelling of 21870117 in words is "twenty-one million, eight hundred seventy thousand, one hundred seventeen".