21658001778 has 40 divisors (see below), whose sum is σ = 55462822272. Its totient is φ = 6188000184.

The previous prime is 21658001753. The next prime is 21658001791. The reversal of 21658001778 is 87710085612.

It is a happy number.

It is a super-2 number, since 2×21658001778² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

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 19 ways as a sum of consecutive naturals, for example, 9548250 + ... + 9550517.

Almost surely, 2^21658001778 is an apocalyptic number.

21658001778 is an abundant number, since it is smaller than the sum of its proper divisors (33804820494).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21658001778 is a wasteful number, since it uses less digits than its factorization.

21658001778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19098788 (or 19098779 counting only the distinct ones).

The product of its (nonzero) digits is 188160, while the sum is 45.

The spelling of 21658001778 in words is "twenty-one billion, six hundred fifty-eight million, one thousand, seven hundred seventy-eight".