21051551387 has 2 divisors, whose sum is σ = 21051551388. Its totient is φ = 21051551386.

The previous prime is 21051551377. The next prime is 21051551447. The reversal of 21051551387 is 78315515012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21051551387 - 2²² = 21047357083 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21051551387.

It is not a weakly prime, because it can be changed into another prime (21051551317) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10525775693 + 10525775694.

It is an arithmetic number, because the mean of its divisors is an integer number (10525775694).

Almost surely, 2^21051551387 is an apocalyptic number.

21051551387 is a deficient number, since it is larger than the sum of its proper divisors (1).

21051551387 is an equidigital number, since it uses as much as digits as its factorization.

21051551387 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 42000, while the sum is 38.

The spelling of 21051551387 in words is "twenty-one billion, fifty-one million, five hundred fifty-one thousand, three hundred eighty-seven".