21252517 has 16 divisors (see below), whose sum is σ = 25099200. Its totient is φ = 17740800.

The previous prime is 21252509. The next prime is 21252547. The reversal of 21252517 is 71525212.

It is not a de Polignac number, because 21252517 - 2³ = 21252509 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21252491 and 21252500.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21252547) 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, 47109 + ... + 47557.

It is an arithmetic number, because the mean of its divisors is an integer number (1568700).

Almost surely, 2^21252517 is an apocalyptic number.

It is an amenable number.

21252517 is a deficient number, since it is larger than the sum of its proper divisors (3846683).

21252517 is a wasteful number, since it uses less digits than its factorization.

21252517 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 804.

The product of its digits is 1400, while the sum is 25.

The square root of 21252517 is about 4610.0452275439. The cubic root of 21252517 is about 276.9938483431.

Adding to 21252517 its reverse (71525212), we get a palindrome (92777729).

The spelling of 21252517 in words is "twenty-one million, two hundred fifty-two thousand, five hundred seventeen".