20191939391 has 4 divisors (see below), whose sum is σ = 21745165512. Its totient is φ = 18638713272.

The previous prime is 20191939381. The next prime is 20191939409. The reversal of 20191939391 is 19393919102.

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 20191939391 - 2¹⁰ = 20191938367 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 (20191939381) 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, 776613041 + ... + 776613066.

It is an arithmetic number, because the mean of its divisors is an integer number (5436291378).

Almost surely, 2^20191939391 is an apocalyptic number.

20191939391 is a deficient number, since it is larger than the sum of its proper divisors (1553226121).

20191939391 is a wasteful number, since it uses less digits than its factorization.

20191939391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1553226120.

The product of its (nonzero) digits is 118098, while the sum is 47.

The spelling of 20191939391 in words is "twenty billion, one hundred ninety-one million, nine hundred thirty-nine thousand, three hundred ninety-one".