21252605 has 8 divisors (see below), whose sum is σ = 27821664. Its totient is φ = 15456400.

The previous prime is 21252593. The next prime is 21252607. The reversal of 21252605 is 50625212.

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

It is not a de Polignac number, because 21252605 - 2⁴ = 21252589 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 (21252607) 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 7 ways as a sum of consecutive naturals, for example, 193151 + ... + 193260.

It is an arithmetic number, because the mean of its divisors is an integer number (3477708).

Almost surely, 2^21252605 is an apocalyptic number.

It is an amenable number.

21252605 is a deficient number, since it is larger than the sum of its proper divisors (6569059).

21252605 is a wasteful number, since it uses less digits than its factorization.

21252605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 386427.

The product of its (nonzero) digits is 1200, while the sum is 23.

The square root of 21252605 is about 4610.0547719089. The cubic root of 21252605 is about 276.9942306574.

Adding to 21252605 its reverse (50625212), we get a palindrome (71877817).

The spelling of 21252605 in words is "twenty-one million, two hundred fifty-two thousand, six hundred five".