21781642288 has 60 divisors (see below), whose sum is σ = 50289484392. Its totient is φ = 9107293440.

The previous prime is 21781642279. The next prime is 21781642291. The reversal of 21781642288 is 88224618712.

It is a hoax number, since the sum of its digits (49) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (49).

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, 306670 + ... + 370957.

Almost surely, 2^21781642288 is an apocalyptic number.

21781642288 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21781642288 is an abundant number, since it is smaller than the sum of its proper divisors (28507842104).

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

21781642288 is a wasteful number, since it uses less digits than its factorization.

21781642288 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 677690 (or 677677 counting only the distinct ones).

The product of its digits is 688128, while the sum is 49.

The spelling of 21781642288 in words is "twenty-one billion, seven hundred eighty-one million, six hundred forty-two thousand, two hundred eighty-eight".