21456347661 has 48 divisors (see below), whose sum is σ = 36797849088. Its totient is φ = 12238743600.

The previous prime is 21456347659. The next prime is 21456347681. The reversal of 21456347661 is 16674365412.

21456347661 is a `hidden beast` number, since 2 + 1 + 4 + 5 + 634 + 7 + 6 + 6 + 1 = 666.

It is not a de Polignac number, because 21456347661 - 2¹ = 21456347659 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21456347621) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 960226 + ... + 982316.

It is an arithmetic number, because the mean of its divisors is an integer number (766621856).

Almost surely, 2^21456347661 is an apocalyptic number.

21456347661 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21456347661 is a deficient number, since it is larger than the sum of its proper divisors (15341501427).

21456347661 is an equidigital number, since it uses as much as digits as its factorization.

21456347661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22684 (or 22672 counting only the distinct ones).

The product of its digits is 725760, while the sum is 45.

The spelling of 21456347661 in words is "twenty-one billion, four hundred fifty-six million, three hundred forty-seven thousand, six hundred sixty-one".