20401391 has 4 divisors (see below), whose sum is σ = 21288432. Its totient is φ = 19514352.

The previous prime is 20401361. The next prime is 20401397. The reversal of 20401391 is 19310402.

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 20401391 - 2¹⁸ = 20139247 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20401397) 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, 443486 + ... + 443531.

It is an arithmetic number, because the mean of its divisors is an integer number (5322108).

Almost surely, 2^20401391 is an apocalyptic number.

20401391 is a deficient number, since it is larger than the sum of its proper divisors (887041).

20401391 is an equidigital number, since it uses as much as digits as its factorization.

20401391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 887040.

The product of its (nonzero) digits is 216, while the sum is 20.

The square root of 20401391 is about 4516.7898999179. The cubic root of 20401391 is about 273.2456518615.

Adding to 20401391 its reverse (19310402), we get a palindrome (39711793).

The spelling of 20401391 in words is "twenty million, four hundred one thousand, three hundred ninety-one".