21297737 has 4 divisors (see below), whose sum is σ = 21817236. Its totient is φ = 20778240.

The previous prime is 21297733. The next prime is 21297751. The reversal of 21297737 is 73779212.

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 6056521 + 15241216 = 2461^2 + 3904^2 .

It is a cyclic number.

It is not a de Polignac number, because 21297737 - 2² = 21297733 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21297737.

It is not an unprimeable number, because it can be changed into a prime (21297733) 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, 259688 + ... + 259769.

It is an arithmetic number, because the mean of its divisors is an integer number (5454309).

Almost surely, 2^21297737 is an apocalyptic number.

It is an amenable number.

21297737 is a deficient number, since it is larger than the sum of its proper divisors (519499).

21297737 is an equidigital number, since it uses as much as digits as its factorization.

21297737 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 519498.

The product of its digits is 37044, while the sum is 38.

The square root of 21297737 is about 4614.9471286246. The cubic root of 21297737 is about 277.1901668700.

The spelling of 21297737 in words is "twenty-one million, two hundred ninety-seven thousand, seven hundred thirty-seven".