21051551441 has 4 divisors (see below), whose sum is σ = 21339928932. Its totient is φ = 20763173952.

The previous prime is 21051551387. The next prime is 21051551447. The reversal of 21051551441 is 14415515012.

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

It can be written as a sum of positive squares in 2 ways, for example, as 5308579600 + 15742971841 = 72860^2 + 125471^2 .

It is a cyclic number.

It is not a de Polignac number, because 21051551441 - 2⁶ = 21051551377 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21051551447) 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, 144188636 + ... + 144188781.

It is an arithmetic number, because the mean of its divisors is an integer number (5334982233).

Almost surely, 2^21051551441 is an apocalyptic number.

It is an amenable number.

21051551441 is a deficient number, since it is larger than the sum of its proper divisors (288377491).

21051551441 is an equidigital number, since it uses as much as digits as its factorization.

21051551441 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 288377490.

The product of its (nonzero) digits is 4000, while the sum is 29.

The spelling of 21051551441 in words is "twenty-one billion, fifty-one million, five hundred fifty-one thousand, four hundred forty-one".