21685910649 has 16 divisors (see below), whose sum is σ = 31193500800. Its totient is φ = 13321708416.

The previous prime is 21685910647. The next prime is 21685910657. The reversal of 21685910649 is 94601958612.

It is not a de Polignac number, because 21685910649 - 2¹ = 21685910647 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21685910647) 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 15 ways as a sum of consecutive naturals, for example, 466429 + ... + 510810.

It is an arithmetic number, because the mean of its divisors is an integer number (1949593800).

Almost surely, 2^21685910649 is an apocalyptic number.

It is an amenable number.

21685910649 is a deficient number, since it is larger than the sum of its proper divisors (9507590151).

21685910649 is a wasteful number, since it uses less digits than its factorization.

21685910649 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 977824.

The product of its (nonzero) digits is 933120, while the sum is 51.

The spelling of 21685910649 in words is "twenty-one billion, six hundred eighty-five million, nine hundred ten thousand, six hundred forty-nine".