21198893821 has 16 divisors (see below), whose sum is σ = 24474939264. Its totient is φ = 17985052224.

The previous prime is 21198893813. The next prime is 21198893857. The reversal of 21198893821 is 12839889112.

It is a cyclic number.

It is not a de Polignac number, because 21198893821 - 2³ = 21198893813 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 (21198893861) 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 15 ways as a sum of consecutive naturals, for example, 896871 + ... + 920203.

It is an arithmetic number, because the mean of its divisors is an integer number (1529683704).

Almost surely, 2^21198893821 is an apocalyptic number.

It is an amenable number.

21198893821 is a deficient number, since it is larger than the sum of its proper divisors (3276045443).

21198893821 is a wasteful number, since it uses less digits than its factorization.

21198893821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24660.

The product of its digits is 497664, while the sum is 52.

It can be divided in two parts, 211988 and 93821, that added together give a square (305809 = 553²).

The spelling of 21198893821 in words is "twenty-one billion, one hundred ninety-eight million, eight hundred ninety-three thousand, eight hundred twenty-one".