20615391 has 14 divisors (see below), whose sum is σ = 30910040. Its totient is φ = 13743108.

The previous prime is 20615363. The next prime is 20615393. The reversal of 20615391 is 19351602.

It is not a de Polignac number, because 20615391 - 2⁵ = 20615359 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20615393) by changing a digit.

It is a polite number, since it can be written in 13 ways as a sum of consecutive naturals, for example, 13411 + ... + 14868.

It is an arithmetic number, because the mean of its divisors is an integer number (2207860).

Almost surely, 2^20615391 is an apocalyptic number.

20615391 is a deficient number, since it is larger than the sum of its proper divisors (10294649).

20615391 is an frugal number, since it uses more digits than its factorization.

20615391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28297 (or 28282 counting only the distinct ones).

The product of its (nonzero) digits is 1620, while the sum is 27.

The square root of 20615391 is about 4540.4174918172. The cubic root of 20615391 is about 274.1977323142.

Adding to 20615391 its reverse (19351602), we get a palindrome (39966993).

The spelling of 20615391 in words is "twenty million, six hundred fifteen thousand, three hundred ninety-one".