21051551447 has 2 divisors, whose sum is σ = 21051551448. Its totient is φ = 21051551446.

The previous prime is 21051551387. The next prime is 21051551449. The reversal of 21051551447 is 74415515012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21051551447 - 2²² = 21047357143 is a prime.

Together with 21051551449, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21051551449) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10525775723 + 10525775724.

It is an arithmetic number, because the mean of its divisors is an integer number (10525775724).

Almost surely, 2^21051551447 is an apocalyptic number.

21051551447 is a deficient number, since it is larger than the sum of its proper divisors (1).

21051551447 is an equidigital number, since it uses as much as digits as its factorization.

21051551447 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 28000, while the sum is 35.

The spelling of 21051551447 in words is "twenty-one billion, fifty-one million, five hundred fifty-one thousand, four hundred forty-seven".