21413251 has 4 divisors (see below), whose sum is σ = 22672872. Its totient is φ = 20153632.

The previous prime is 21413243. The next prime is 21413279. The reversal of 21413251 is 15231412.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21413251 - 2³ = 21413243 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21413221) 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, 629785 + ... + 629818.

It is an arithmetic number, because the mean of its divisors is an integer number (5668218).

Almost surely, 2^21413251 is an apocalyptic number.

21413251 is a deficient number, since it is larger than the sum of its proper divisors (1259621).

21413251 is a wasteful number, since it uses less digits than its factorization.

21413251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1259620.

The product of its digits is 240, while the sum is 19.

The square root of 21413251 is about 4627.4454075656. The cubic root of 21413251 is about 277.6904020238.

Adding to 21413251 its reverse (15231412), we get a palindrome (36644663).

The spelling of 21413251 in words is "twenty-one million, four hundred thirteen thousand, two hundred fifty-one".