21253617 has 32 divisors (see below), whose sum is σ = 39260160. Its totient is φ = 11039760.

The previous prime is 21253613. The next prime is 21253627. The reversal of 21253617 is 71635212.

It is a happy number.

21253617 is a `hidden beast` number, since 21 + 25 + 3 + 617 = 666.

It is not a de Polignac number, because 21253617 - 2² = 21253613 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21253613) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 3033 + ... + 7190.

It is an arithmetic number, because the mean of its divisors is an integer number (1226880).

Almost surely, 2^21253617 is an apocalyptic number.

21253617 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21253617 is a deficient number, since it is larger than the sum of its proper divisors (18006543).

21253617 is a wasteful number, since it uses less digits than its factorization.

21253617 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10250 (or 10244 counting only the distinct ones).

The product of its digits is 2520, while the sum is 27.

The square root of 21253617 is about 4610.1645306865. The cubic root of 21253617 is about 276.9986271963.

Adding to 21253617 its reverse (71635212), we get a palindrome (92888829).

The spelling of 21253617 in words is "twenty-one million, two hundred fifty-three thousand, six hundred seventeen".