21451373257 has 4 divisors (see below), whose sum is σ = 21453440976. Its totient is φ = 21449305540.

The previous prime is 21451373249. The next prime is 21451373261. The reversal of 21451373257 is 75237315412.

It is a happy number.

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 21451373257 - 2³ = 21451373249 is a prime.

It is a super-2 number, since 2×21451373257² (a number of 21 digits) contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21451373227) 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, 1018219 + ... + 1039072.

It is an arithmetic number, because the mean of its divisors is an integer number (5363360244).

Almost surely, 2^21451373257 is an apocalyptic number.

It is an amenable number.

21451373257 is a deficient number, since it is larger than the sum of its proper divisors (2067719).

21451373257 is a wasteful number, since it uses less digits than its factorization.

21451373257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2067718.

The product of its digits is 176400, while the sum is 40.

Adding to 21451373257 its reverse (75237315412), we get a palindrome (96688688669).

The spelling of 21451373257 in words is "twenty-one billion, four hundred fifty-one million, three hundred seventy-three thousand, two hundred fifty-seven".