21647126778 has 32 divisors (see below), whose sum is σ = 45675878400. Its totient is φ = 6820487856.

The previous prime is 21647126771. The next prime is 21647126801. The reversal of 21647126778 is 87762174612.

It is a super-2 number, since 2×21647126778² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21647126778.

It is not an unprimeable number, because it can be changed into a prime (21647126771) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 163818 + ... + 264821.

It is an arithmetic number, because the mean of its divisors is an integer number (1427371200).

Almost surely, 2^21647126778 is an apocalyptic number.

21647126778 is an abundant number, since it is smaller than the sum of its proper divisors (24028751622).

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

21647126778 is a wasteful number, since it uses less digits than its factorization.

21647126778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 429106.

The product of its digits is 1580544, while the sum is 51.

The spelling of 21647126778 in words is "twenty-one billion, six hundred forty-seven million, one hundred twenty-six thousand, seven hundred seventy-eight".