21253451 has 4 divisors (see below), whose sum is σ = 22503672. Its totient is φ = 20003232.

The previous prime is 21253423. The next prime is 21253459. The reversal of 21253451 is 15435212.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21253451 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21253459) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 625085 + ... + 625118.

It is an arithmetic number, because the mean of its divisors is an integer number (5625918).

Almost surely, 2^21253451 is an apocalyptic number.

21253451 is a deficient number, since it is larger than the sum of its proper divisors (1250221).

21253451 is a wasteful number, since it uses less digits than its factorization.

21253451 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1250220.

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

The square root of 21253451 is about 4610.1465269555. The cubic root of 21253451 is about 276.9979060345.

Adding to 21253451 its reverse (15435212), we get a palindrome (36688663).

The spelling of 21253451 in words is "twenty-one million, two hundred fifty-three thousand, four hundred fifty-one".