21821451 has 4 divisors (see below), whose sum is σ = 29095272. Its totient is φ = 14547632.

The previous prime is 21821441. The next prime is 21821461. The reversal of 21821451 is 15412812.

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

It is an interprime number because it is at equal distance from previous prime (21821441) and next prime (21821461).

It is a cyclic number.

It is not a de Polignac number, because 21821451 - 2⁵ = 21821419 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21821441) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3636906 + ... + 3636911.

It is an arithmetic number, because the mean of its divisors is an integer number (7273818).

Almost surely, 2^21821451 is an apocalyptic number.

21821451 is a deficient number, since it is larger than the sum of its proper divisors (7273821).

21821451 is an equidigital number, since it uses as much as digits as its factorization.

21821451 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7273820.

The product of its digits is 640, while the sum is 24.

The square root of 21821451 is about 4671.3435968680. The cubic root of 21821451 is about 279.4438407697.

The spelling of 21821451 in words is "twenty-one million, eight hundred twenty-one thousand, four hundred fifty-one".