21770145 has 24 divisors (see below), whose sum is σ = 37865256. Its totient is φ = 11570688.

The previous prime is 21770141. The next prime is 21770179. The reversal of 21770145 is 54107712.

It can be written as a sum of positive squares in 4 ways, for example, as 9217296 + 12552849 = 3036^2 + 3543^2 .

It is not a de Polignac number, because 21770145 - 2² = 21770141 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21770141) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 16137 + ... + 17433.

It is an arithmetic number, because the mean of its divisors is an integer number (1577719).

Almost surely, 2^21770145 is an apocalyptic number.

It is an amenable number.

21770145 is a deficient number, since it is larger than the sum of its proper divisors (16095111).

21770145 is a wasteful number, since it uses less digits than its factorization.

21770145 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1681 (or 1678 counting only the distinct ones).

The product of its (nonzero) digits is 1960, while the sum is 27.

The square root of 21770145 is about 4665.8487973787. The cubic root of 21770145 is about 279.2246619937.

Adding to 21770145 its reverse (54107712), we get a palindrome (75877857).

The spelling of 21770145 in words is "twenty-one million, seven hundred seventy thousand, one hundred forty-five".