21971545 has 4 divisors (see below), whose sum is σ = 26365860. Its totient is φ = 17577232.

The previous prime is 21971539. The next prime is 21971549. The reversal of 21971545 is 54517912.

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 11916304 + 10055241 = 3452^2 + 3171^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21971545 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21971545.

It is not an unprimeable number, because it can be changed into a prime (21971549) 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, 2197150 + ... + 2197159.

It is an arithmetic number, because the mean of its divisors is an integer number (6591465).

Almost surely, 2^21971545 is an apocalyptic number.

It is an amenable number.

21971545 is a deficient number, since it is larger than the sum of its proper divisors (4394315).

21971545 is an equidigital number, since it uses as much as digits as its factorization.

21971545 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4394314.

The product of its digits is 12600, while the sum is 34.

The square root of 21971545 is about 4687.3814651679. The cubic root of 21971545 is about 280.0830748394.

The spelling of 21971545 in words is "twenty-one million, nine hundred seventy-one thousand, five hundred forty-five".