21965257 has 4 divisors (see below), whose sum is σ = 21981136. Its totient is φ = 21949380.

The previous prime is 21965249. The next prime is 21965351. The reversal of 21965257 is 75256912.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21965257 - 2³ = 21965249 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21965227) 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 3 ways as a sum of consecutive naturals, for example, 5643 + ... + 8704.

It is an arithmetic number, because the mean of its divisors is an integer number (5495284).

Almost surely, 2^21965257 is an apocalyptic number.

It is an amenable number.

21965257 is a deficient number, since it is larger than the sum of its proper divisors (15879).

21965257 is a wasteful number, since it uses less digits than its factorization.

21965257 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15878.

The product of its digits is 37800, while the sum is 37.

The square root of 21965257 is about 4686.7106802106. The cubic root of 21965257 is about 280.0563534533.

It can be divided in two parts, 21965 and 257, that added together give a palindrome (22222).

The spelling of 21965257 in words is "twenty-one million, nine hundred sixty-five thousand, two hundred fifty-seven".