21787047871 has 4 divisors (see below), whose sum is σ = 21801078432. Its totient is φ = 21773017312.

The previous prime is 21787047869. The next prime is 21787047881. The reversal of 21787047871 is 17874078712.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21787047871 - 2¹ = 21787047869 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21787047811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7012951 + ... + 7016056.

It is an arithmetic number, because the mean of its divisors is an integer number (5450269608).

Almost surely, 2^21787047871 is an apocalyptic number.

21787047871 is a deficient number, since it is larger than the sum of its proper divisors (14030561).

21787047871 is a wasteful number, since it uses less digits than its factorization.

21787047871 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14030560.

The product of its (nonzero) digits is 1229312, while the sum is 52.

The spelling of 21787047871 in words is "twenty-one billion, seven hundred eighty-seven million, forty-seven thousand, eight hundred seventy-one".