21085155457 has 2 divisors, whose sum is σ = 21085155458. Its totient is φ = 21085155456.

The previous prime is 21085155433. The next prime is 21085155473. The reversal of 21085155457 is 75455158012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20111777856 + 973377601 = 141816^2 + 31199^2 .

It is a cyclic number.

It is not a de Polignac number, because 21085155457 - 2²³ = 21076766849 is a prime.

It is not a weakly prime, because it can be changed into another prime (21085159457) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10542577728 + 10542577729.

It is an arithmetic number, because the mean of its divisors is an integer number (10542577729).

Almost surely, 2^21085155457 is an apocalyptic number.

It is an amenable number.

21085155457 is a deficient number, since it is larger than the sum of its proper divisors (1).

21085155457 is an equidigital number, since it uses as much as digits as its factorization.

21085155457 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 280000, while the sum is 43.

The spelling of 21085155457 in words is "twenty-one billion, eighty-five million, one hundred fifty-five thousand, four hundred fifty-seven".