21042521281 has 4 divisors (see below), whose sum is σ = 21067966512. Its totient is φ = 21017076052.

The previous prime is 21042521251. The next prime is 21042521303. The reversal of 21042521281 is 18212524012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21042521281 - 2²³ = 21034132673 is a prime.

It is a super-2 number, since 2×21042521281² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21042521251) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12721375 + ... + 12723028.

It is an arithmetic number, because the mean of its divisors is an integer number (5266991628).

Almost surely, 2^21042521281 is an apocalyptic number.

It is an amenable number.

21042521281 is a deficient number, since it is larger than the sum of its proper divisors (25445231).

21042521281 is an equidigital number, since it uses as much as digits as its factorization.

21042521281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25445230.

The product of its (nonzero) digits is 2560, while the sum is 28.

The spelling of 21042521281 in words is "twenty-one billion, forty-two million, five hundred twenty-one thousand, two hundred eighty-one".