21085664401 has 4 divisors (see below), whose sum is σ = 21090845412. Its totient is φ = 21080483392.

The previous prime is 21085664399. The next prime is 21085664429. The reversal of 21085664401 is 10446658012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10139483025 + 10946181376 = 100695^2 + 104624^2 .

It is a cyclic number.

It is not a de Polignac number, because 21085664401 - 2¹ = 21085664399 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21085664441) 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 in 3 ways as a sum of consecutive naturals, for example, 2584396 + ... + 2592541.

It is an arithmetic number, because the mean of its divisors is an integer number (5272711353).

Almost surely, 2^21085664401 is an apocalyptic number.

It is an amenable number.

21085664401 is a deficient number, since it is larger than the sum of its proper divisors (5181011).

21085664401 is an equidigital number, since it uses as much as digits as its factorization.

21085664401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5181010.

The product of its (nonzero) digits is 46080, while the sum is 37.

The spelling of 21085664401 in words is "twenty-one billion, eighty-five million, six hundred sixty-four thousand, four hundred one".