21054757891 has 2 divisors, whose sum is σ = 21054757892. Its totient is φ = 21054757890.

The previous prime is 21054757859. The next prime is 21054757937. The reversal of 21054757891 is 19875745012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21054757891 - 2⁵ = 21054757859 is a prime.

It is not a weakly prime, because it can be changed into another prime (21054757391) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10527378945 + 10527378946.

It is an arithmetic number, because the mean of its divisors is an integer number (10527378946).

Almost surely, 2^21054757891 is an apocalyptic number.

21054757891 is a deficient number, since it is larger than the sum of its proper divisors (1).

21054757891 is an equidigital number, since it uses as much as digits as its factorization.

21054757891 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 705600, while the sum is 49.

The spelling of 21054757891 in words is "twenty-one billion, fifty-four million, seven hundred fifty-seven thousand, eight hundred ninety-one".