21821896391 has 4 divisors (see below), whose sum is σ = 21823014984. Its totient is φ = 21820777800.

The previous prime is 21821896387. The next prime is 21821896403. The reversal of 21821896391 is 19369812812.

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 21821896391 - 2² = 21821896387 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 (21821896361) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 529505 + ... + 569226.

It is an arithmetic number, because the mean of its divisors is an integer number (5455753746).

Almost surely, 2^21821896391 is an apocalyptic number.

21821896391 is a deficient number, since it is larger than the sum of its proper divisors (1118593).

21821896391 is a wasteful number, since it uses less digits than its factorization.

21821896391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1118592.

The product of its digits is 373248, while the sum is 50.

The spelling of 21821896391 in words is "twenty-one billion, eight hundred twenty-one million, eight hundred ninety-six thousand, three hundred ninety-one".