21352257 has 48 divisors (see below), whose sum is σ = 34819200. Its totient is φ = 12545280.

The previous prime is 21352249. The next prime is 21352291. The reversal of 21352257 is 75225312.

It is not a de Polignac number, because 21352257 - 2³ = 21352249 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21352257.

It is not an unprimeable number, because it can be changed into a prime (21352217) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 239869 + ... + 239957.

It is an arithmetic number, because the mean of its divisors is an integer number (725400).

Almost surely, 2^21352257 is an apocalyptic number.

It is an amenable number.

21352257 is a deficient number, since it is larger than the sum of its proper divisors (13466943).

21352257 is a wasteful number, since it uses less digits than its factorization.

21352257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 198 (or 195 counting only the distinct ones).

The product of its digits is 4200, while the sum is 27.

The square root of 21352257 is about 4620.8502464373. The cubic root of 21352257 is about 277.4264913647.

Adding to 21352257 its reverse (75225312), we get a palindrome (96577569).

It can be divided in two parts, 21352 and 257, that added together give a square (21609 = 147²).

The spelling of 21352257 in words is "twenty-one million, three hundred fifty-two thousand, two hundred fifty-seven".