21197028391 has 24 divisors (see below), whose sum is σ = 28073494656. Its totient is φ = 15545550720.

The previous prime is 21197028389. The next prime is 21197028401. The reversal of 21197028391 is 19382079112.

It is not a de Polignac number, because 21197028391 - 2¹ = 21197028389 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 (21197028361) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 454021 + ... + 498526.

It is an arithmetic number, because the mean of its divisors is an integer number (1169728944).

Almost surely, 2^21197028391 is an apocalyptic number.

21197028391 is a deficient number, since it is larger than the sum of its proper divisors (6876466265).

21197028391 is a wasteful number, since it uses less digits than its factorization.

21197028391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 952599 (or 952582 counting only the distinct ones).

The product of its (nonzero) digits is 54432, while the sum is 43.

The spelling of 21197028391 in words is "twenty-one billion, one hundred ninety-seven million, twenty-eight thousand, three hundred ninety-one".