20715391 has 4 divisors (see below), whose sum is σ = 21156192. Its totient is φ = 20274592.

The previous prime is 20715349. The next prime is 20715407. The reversal of 20715391 is 19351702.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20715391 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 (20715091) 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, 220330 + ... + 220423.

It is an arithmetic number, because the mean of its divisors is an integer number (5289048).

Almost surely, 2^20715391 is an apocalyptic number.

20715391 is a deficient number, since it is larger than the sum of its proper divisors (440801).

20715391 is an equidigital number, since it uses as much as digits as its factorization.

20715391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 440800.

The product of its (nonzero) digits is 1890, while the sum is 28.

The square root of 20715391 is about 4551.4163729547. The cubic root of 20715391 is about 274.6403717784.

The spelling of 20715391 in words is "twenty million, seven hundred fifteen thousand, three hundred ninety-one".