21234201257 has 4 divisors (see below), whose sum is σ = 21234915780. Its totient is φ = 21233486736.

The previous prime is 21234201221. The next prime is 21234201269. The reversal of 21234201257 is 75210243212.

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 7691991616 + 13542209641 = 87704^2 + 116371^2 .

It is a cyclic number.

It is not a de Polignac number, because 21234201257 - 2⁶ = 21234201193 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21234209257) 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, 310658 + ... + 372795.

It is an arithmetic number, because the mean of its divisors is an integer number (5308728945).

Almost surely, 2^21234201257 is an apocalyptic number.

It is an amenable number.

21234201257 is a deficient number, since it is larger than the sum of its proper divisors (714523).

21234201257 is an equidigital number, since it uses as much as digits as its factorization.

21234201257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 714522.

The product of its (nonzero) digits is 6720, while the sum is 29.

Adding to 21234201257 its reverse (75210243212), we get a palindrome (96444444469).

The spelling of 21234201257 in words is "twenty-one billion, two hundred thirty-four million, two hundred one thousand, two hundred fifty-seven".