21405361968 has 100 divisors (see below), whose sum is σ = 62312092128. Its totient is φ = 7093802880.

The previous prime is 21405361927. The next prime is 21405361969. The reversal of 21405361968 is 86916350412.

21405361968 is a `hidden beast` number, since 2 + 1 + 40 + 536 + 19 + 68 = 666.

It is a super-2 number, since 2×21405361968² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21405361969) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 176473 + ... + 271943.

Almost surely, 2^21405361968 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21405361968, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31156046064).

21405361968 is an abundant number, since it is smaller than the sum of its proper divisors (40906730160).

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

21405361968 is a wasteful number, since it uses less digits than its factorization.

21405361968 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 95664 (or 95649 counting only the distinct ones).

The product of its (nonzero) digits is 311040, while the sum is 45.

The spelling of 21405361968 in words is "twenty-one billion, four hundred five million, three hundred sixty-one thousand, nine hundred sixty-eight".