21025451 has 4 divisors (see below), whose sum is σ = 21089304. Its totient is φ = 20961600.

The previous prime is 21025439. The next prime is 21025469. The reversal of 21025451 is 15452012.

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 21025451 - 2¹⁴ = 21009067 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21025051) 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, 31430 + ... + 32091.

It is an arithmetic number, because the mean of its divisors is an integer number (5272326).

Almost surely, 2^21025451 is an apocalyptic number.

21025451 is a deficient number, since it is larger than the sum of its proper divisors (63853).

21025451 is an equidigital number, since it uses as much as digits as its factorization.

21025451 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 63852.

The product of its (nonzero) digits is 400, while the sum is 20.

The square root of 21025451 is about 4585.3517858502. The cubic root of 21025451 is about 276.0038287994.

Adding to 21025451 its reverse (15452012), we get a palindrome (36477463).

The spelling of 21025451 in words is "twenty-one million, twenty-five thousand, four hundred fifty-one".