21537097 has 4 divisors (see below), whose sum is σ = 21588676. Its totient is φ = 21485520.

The previous prime is 21537091. The next prime is 21537107. The reversal of 21537097 is 79073512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10653696 + 10883401 = 3264^2 + 3299^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21537097 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21537091) 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, 25158 + ... + 25999.

It is an arithmetic number, because the mean of its divisors is an integer number (5397169).

Almost surely, 2^21537097 is an apocalyptic number.

It is an amenable number.

21537097 is a deficient number, since it is larger than the sum of its proper divisors (51579).

21537097 is an equidigital number, since it uses as much as digits as its factorization.

21537097 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51578.

The product of its (nonzero) digits is 13230, while the sum is 34.

The square root of 21537097 is about 4640.8077960631. The cubic root of 21537097 is about 278.2247246979.

The spelling of 21537097 in words is "twenty-one million, five hundred thirty-seven thousand, ninety-seven".