21651655671 has 20 divisors (see below), whose sum is σ = 33217993512. Its totient is φ = 14044315248.

The previous prime is 21651655633. The next prime is 21651655691. The reversal of 21651655671 is 17655615612.

It is a happy number.

21651655671 is a `hidden beast` number, since 2 + 16 + 5 + 16 + 556 + 71 = 666.

It is not a de Polignac number, because 21651655671 - 2⁶ = 21651655607 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21651655621) 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 19 ways as a sum of consecutive naturals, for example, 3609225 + ... + 3615218.

Almost surely, 2^21651655671 is an apocalyptic number.

21651655671 is a deficient number, since it is larger than the sum of its proper divisors (11566337841).

21651655671 is an equidigital number, since it uses as much as digits as its factorization.

21651655671 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7224492 (or 7224483 counting only the distinct ones).

The product of its digits is 378000, while the sum is 45.

The spelling of 21651655671 in words is "twenty-one billion, six hundred fifty-one million, six hundred fifty-five thousand, six hundred seventy-one".