21371591 has 2 divisors, whose sum is σ = 21371592. Its totient is φ = 21371590.

The previous prime is 21371569. The next prime is 21371627. The reversal of 21371591 is 19517312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21371591 - 2¹⁴ = 21355207 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21371551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10685795 + 10685796.

It is an arithmetic number, because the mean of its divisors is an integer number (10685796).

Almost surely, 2^21371591 is an apocalyptic number.

21371591 is a deficient number, since it is larger than the sum of its proper divisors (1).

21371591 is an equidigital number, since it uses as much as digits as its factorization.

21371591 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1890, while the sum is 29.

The square root of 21371591 is about 4622.9418123096. The cubic root of 21371591 is about 277.5102006369.

The spelling of 21371591 in words is "twenty-one million, three hundred seventy-one thousand, five hundred ninety-one".