21345306257 has 4 divisors (see below), whose sum is σ = 23285788656. Its totient is φ = 19404823860.

The previous prime is 21345306251. The next prime is 21345306313. The reversal of 21345306257 is 75260354312.

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 21345306257 - 2¹² = 21345302161 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21345306257.

It is not an unprimeable number, because it can be changed into a prime (21345306251) 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, 970241183 + ... + 970241204.

It is an arithmetic number, because the mean of its divisors is an integer number (5821447164).

Almost surely, 2^21345306257 is an apocalyptic number.

It is an amenable number.

21345306257 is a deficient number, since it is larger than the sum of its proper divisors (1940482399).

21345306257 is a wasteful number, since it uses less digits than its factorization.

21345306257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1940482398.

The product of its (nonzero) digits is 151200, while the sum is 38.

The spelling of 21345306257 in words is "twenty-one billion, three hundred forty-five million, three hundred six thousand, two hundred fifty-seven".