21216361515451 has 2 divisors, whose sum is σ = 21216361515452. Its totient is φ = 21216361515450.

The previous prime is 21216361515407. The next prime is 21216361515529. The reversal of 21216361515451 is 15451516361212.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21216361515451 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21216361515398 and 21216361515407.

It is not a weakly prime, because it can be changed into another prime (21216361615451) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10608180757725 + 10608180757726.

It is an arithmetic number, because the mean of its divisors is an integer number (10608180757726).

Almost surely, 2^{21216361515451} is an apocalyptic number.

21216361515451 is a deficient number, since it is larger than the sum of its proper divisors (1).

21216361515451 is an equidigital number, since it uses as much as digits as its factorization.

21216361515451 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 216000, while the sum is 43.

Adding to 21216361515451 its reverse (15451516361212), we get a palindrome (36667877876663).

The spelling of 21216361515451 in words is "twenty-one trillion, two hundred sixteen billion, three hundred sixty-one million, five hundred fifteen thousand, four hundred fifty-one".