20821874391 has 16 divisors (see below), whose sum is σ = 31564600320. Its totient is φ = 13558429080.

The previous prime is 20821874371. The next prime is 20821874393. The reversal of 20821874391 is 19347812802.

It is a happy number.

20821874391 is a `hidden beast` number, since 2 + 0 + 82 + 187 + 4 + 391 = 666.

It is not a de Polignac number, because 20821874391 - 2¹⁰ = 20821873367 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20821874393) 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, 8966055 + ... + 8968376.

It is an arithmetic number, because the mean of its divisors is an integer number (1972787520).

Almost surely, 2^20821874391 is an apocalyptic number.

20821874391 is a deficient number, since it is larger than the sum of its proper divisors (10742725929).

20821874391 is a wasteful number, since it uses less digits than its factorization.

20821874391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17934483 (or 17934477 counting only the distinct ones).

The product of its (nonzero) digits is 193536, while the sum is 45.

The spelling of 20821874391 in words is "twenty billion, eight hundred twenty-one million, eight hundred seventy-four thousand, three hundred ninety-one".