21315451 has 2 divisors, whose sum is σ = 21315452. Its totient is φ = 21315450.

The previous prime is 21315443. The next prime is 21315491. The reversal of 21315451 is 15451312.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21315451 - 2³ = 21315443 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21315421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10657725 + 10657726.

It is an arithmetic number, because the mean of its divisors is an integer number (10657726).

Almost surely, 2^21315451 is an apocalyptic number.

21315451 is a deficient number, since it is larger than the sum of its proper divisors (1).

21315451 is an equidigital number, since it uses as much as digits as its factorization.

21315451 is an evil number, because the sum of its binary digits is even.

The product of its digits is 600, while the sum is 22.

The square root of 21315451 is about 4616.8659283111. The cubic root of 21315451 is about 277.2669948437.

Adding to 21315451 its reverse (15451312), we get a palindrome (36766763).

The spelling of 21315451 in words is "twenty-one million, three hundred fifteen thousand, four hundred fifty-one".