21787871099 has 4 divisors (see below), whose sum is σ = 21804671064. Its totient is φ = 21771071136.

The previous prime is 21787871069. The next prime is 21787871101. The reversal of 21787871099 is 99017878712.

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 21787871099 - 2²⁰ = 21786822523 is a prime.

It is a super-2 number, since 2×21787871099² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21787871009) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8398037 + ... + 8400630.

It is an arithmetic number, because the mean of its divisors is an integer number (5451167766).

Almost surely, 2^21787871099 is an apocalyptic number.

21787871099 is a deficient number, since it is larger than the sum of its proper divisors (16799965).

21787871099 is a wasteful number, since it uses less digits than its factorization.

21787871099 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16799964.

The product of its (nonzero) digits is 3556224, while the sum is 59.

The spelling of 21787871099 in words is "twenty-one billion, seven hundred eighty-seven million, eight hundred seventy-one thousand, ninety-nine".