21724833978 has 24 divisors (see below), whose sum is σ = 47090586816. Its totient is φ = 7238517000.

The previous prime is 21724833973. The next prime is 21724833983. The reversal of 21724833978 is 87933842712.

21724833978 is a `hidden beast` number, since 2 + 1 + 7 + 248 + 3 + 397 + 8 = 666.

It is an interprime number because it is at equal distance from previous prime (21724833973) and next prime (21724833983).

It is a super-2 number, since 2×21724833978² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21724833973) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 214368 + ... + 299003.

It is an arithmetic number, because the mean of its divisors is an integer number (1962107784).

Almost surely, 2^21724833978 is an apocalyptic number.

21724833978 is an abundant number, since it is smaller than the sum of its proper divisors (25365752838).

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

21724833978 is a wasteful number, since it uses less digits than its factorization.

21724833978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 515730 (or 515727 counting only the distinct ones).

The product of its digits is 4064256, while the sum is 54.

The spelling of 21724833978 in words is "twenty-one billion, seven hundred twenty-four million, eight hundred thirty-three thousand, nine hundred seventy-eight".