21449388557 has 4 divisors (see below), whose sum is σ = 21452523516. Its totient is φ = 21446253600.

The previous prime is 21449388551. The next prime is 21449388559. The reversal of 21449388557 is 75588394412.

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 2210034121 + 19239354436 = 47011^2 + 138706^2 .

It is a cyclic number.

It is not a de Polignac number, because 21449388557 - 2¹² = 21449384461 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21449388551) 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, 1557194 + ... + 1570907.

It is an arithmetic number, because the mean of its divisors is an integer number (5363130879).

Almost surely, 2^21449388557 is an apocalyptic number.

It is an amenable number.

21449388557 is a deficient number, since it is larger than the sum of its proper divisors (3134959).

21449388557 is an equidigital number, since it uses as much as digits as its factorization.

21449388557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3134958.

The product of its digits is 9676800, while the sum is 56.

The spelling of 21449388557 in words is "twenty-one billion, four hundred forty-nine million, three hundred eighty-eight thousand, five hundred fifty-seven".