21203134391 has 4 divisors (see below), whose sum is σ = 21271311984. Its totient is φ = 21134956800.

The previous prime is 21203134369. The next prime is 21203134411. The reversal of 21203134391 is 19343130212.

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 21203134391 - 2¹⁴ = 21203118007 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 (21203134301) 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 3 ways as a sum of consecutive naturals, for example, 34088330 + ... + 34088951.

It is an arithmetic number, because the mean of its divisors is an integer number (5317827996).

Almost surely, 2^21203134391 is an apocalyptic number.

21203134391 is a deficient number, since it is larger than the sum of its proper divisors (68177593).

21203134391 is an equidigital number, since it uses as much as digits as its factorization.

21203134391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 68177592.

The product of its (nonzero) digits is 3888, while the sum is 29.

The spelling of 21203134391 in words is "twenty-one billion, two hundred three million, one hundred thirty-four thousand, three hundred ninety-one".