21542661504 has 896 divisors, whose sum is σ = 82410451200. Its totient is φ = 5455392768.

The previous prime is 21542661433. The next prime is 21542661509. The reversal of 21542661504 is 40516624512.

21542661504 is a `hidden beast` number, since 2 + 1 + 542 + 6 + 61 + 50 + 4 = 666.

It is a tau number, because it is divible by the number of its divisors (896).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21542661509) by changing a digit.

It is a polite number, since it can be written in 111 ways as a sum of consecutive naturals, for example, 365129827 + ... + 365129885.

It is an arithmetic number, because the mean of its divisors is an integer number (91975950).

Almost surely, 2^21542661504 is an apocalyptic number.

21542661504 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21542661504, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41205225600).

21542661504 is an abundant number, since it is smaller than the sum of its proper divisors (60867789696).

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

21542661504 is an equidigital number, since it uses as much as digits as its factorization.

21542661504 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 154 (or 127 counting only the distinct ones).

The product of its (nonzero) digits is 57600, while the sum is 36.

The spelling of 21542661504 in words is "twenty-one billion, five hundred forty-two million, six hundred sixty-one thousand, five hundred four".