21085284251 has 2 divisors, whose sum is σ = 21085284252. Its totient is φ = 21085284250.

The previous prime is 21085284211. The next prime is 21085284271. The reversal of 21085284251 is 15248258012.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21085284251 is a prime.

It is not a weakly prime, because it can be changed into another prime (21085284211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10542642125 + 10542642126.

It is an arithmetic number, because the mean of its divisors is an integer number (10542642126).

Almost surely, 2^21085284251 is an apocalyptic number.

21085284251 is a deficient number, since it is larger than the sum of its proper divisors (1).

21085284251 is an equidigital number, since it uses as much as digits as its factorization.

21085284251 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 51200, while the sum is 38.

The spelling of 21085284251 in words is "twenty-one billion, eighty-five million, two hundred eighty-four thousand, two hundred fifty-one".