21540681468 has 36 divisors (see below), whose sum is σ = 54815506200. Its totient is φ = 7132035936.

The previous prime is 21540681431. The next prime is 21540681493. The reversal of 21540681468 is 86418604512.

It is a happy number.

21540681468 is a `hidden beast` number, since 2 + 1 + 540 + 68 + 1 + 46 + 8 = 666.

It is a tau number, because it is divible by the number of its divisors (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2002530 + ... + 2013257.

It is an arithmetic number, because the mean of its divisors is an integer number (1522652950).

Almost surely, 2^21540681468 is an apocalyptic number.

It is an amenable number.

21540681468 is an abundant number, since it is smaller than the sum of its proper divisors (33274824732).

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

21540681468 is a wasteful number, since it uses less digits than its factorization.

21540681468 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4015946 (or 4015941 counting only the distinct ones).

The product of its (nonzero) digits is 368640, while the sum is 45.

The spelling of 21540681468 in words is "twenty-one billion, five hundred forty million, six hundred eighty-one thousand, four hundred sixty-eight".