21361591 has 2 divisors, whose sum is σ = 21361592. Its totient is φ = 21361590.

The previous prime is 21361579. The next prime is 21361609. The reversal of 21361591 is 19516312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21361591 - 2⁷ = 21361463 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21361091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10680795 + 10680796.

It is an arithmetic number, because the mean of its divisors is an integer number (10680796).

Almost surely, 2^21361591 is an apocalyptic number.

21361591 is a deficient number, since it is larger than the sum of its proper divisors (1).

21361591 is an equidigital number, since it uses as much as digits as its factorization.

21361591 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1620, while the sum is 28.

The square root of 21361591 is about 4621.8601233702. The cubic root of 21361591 is about 277.4669105366.

It can be divided in two parts, 21361 and 591, that added together give a cube (21952 = 28³).

The spelling of 21361591 in words is "twenty-one million, three hundred sixty-one thousand, five hundred ninety-one".