21537191 has 8 divisors (see below), whose sum is σ = 23333520. Its totient is φ = 19878456.

The previous prime is 21537179. The next prime is 21537251. The reversal of 21537191 is 19173512.

It is not a de Polignac number, because 21537191 - 2²² = 17342887 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21537121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2705 + ... + 7098.

It is an arithmetic number, because the mean of its divisors is an integer number (2916690).

Almost surely, 2^21537191 is an apocalyptic number.

21537191 is a deficient number, since it is larger than the sum of its proper divisors (1796329).

21537191 is an frugal number, since it uses more digits than its factorization.

21537191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9842 (or 9816 counting only the distinct ones).

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

The square root of 21537191 is about 4640.8179235992. The cubic root of 21537191 is about 278.2251294737.

The spelling of 21537191 in words is "twenty-one million, five hundred thirty-seven thousand, one hundred ninety-one".