20261591 has 4 divisors (see below), whose sum is σ = 23156112. Its totient is φ = 17367072.

The previous prime is 20261567. The next prime is 20261599. The reversal of 20261591 is 19516202.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19516202 = 2 ⋅9758101.

It is a cyclic number.

It is not a de Polignac number, because 20261591 - 2¹⁰ = 20260567 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20261591.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20261599) 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, 1447250 + ... + 1447263.

It is an arithmetic number, because the mean of its divisors is an integer number (5789028).

Almost surely, 2^20261591 is an apocalyptic number.

20261591 is a deficient number, since it is larger than the sum of its proper divisors (2894521).

20261591 is an equidigital number, since it uses as much as digits as its factorization.

20261591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2894520.

The product of its (nonzero) digits is 1080, while the sum is 26.

The square root of 20261591 is about 4501.2877046463. The cubic root of 20261591 is about 272.6200845481.

Adding to 20261591 its reverse (19516202), we get a palindrome (39777793).

The spelling of 20261591 in words is "twenty million, two hundred sixty-one thousand, five hundred ninety-one".