21123253387 has 2 divisors, whose sum is σ = 21123253388. Its totient is φ = 21123253386.

The previous prime is 21123253369. The next prime is 21123253427. The reversal of 21123253387 is 78335232112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21123253387 - 2¹¹ = 21123251339 is a prime.

It is not a weakly prime, because it can be changed into another prime (21123253367) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10561626693 + 10561626694.

It is an arithmetic number, because the mean of its divisors is an integer number (10561626694).

Almost surely, 2^21123253387 is an apocalyptic number.

21123253387 is a deficient number, since it is larger than the sum of its proper divisors (1).

21123253387 is an equidigital number, since it uses as much as digits as its factorization.

21123253387 is an evil number, because the sum of its binary digits is even.

The product of its digits is 60480, while the sum is 37.

Adding to 21123253387 its reverse (78335232112), we get a palindrome (99458485499).

The spelling of 21123253387 in words is "twenty-one billion, one hundred twenty-three million, two hundred fifty-three thousand, three hundred eighty-seven".