21007170 has 48 divisors (see below), whose sum is σ = 55960632. Its totient is φ = 5464320.

The previous prime is 21007153. The next prime is 21007171. The reversal of 21007170 is 7170012.

It can be written as a sum of positive squares in 4 ways, for example, as 6922161 + 14085009 = 2631^2 + 3753^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21007171) 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, 844 + ... + 6536.

Almost surely, 2^21007170 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21007170, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27980316).

21007170 is an abundant number, since it is smaller than the sum of its proper divisors (34953462).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21007170 is a wasteful number, since it uses less digits than its factorization.

21007170 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5747 (or 5744 counting only the distinct ones).

The product of its (nonzero) digits is 98, while the sum is 18.

The square root of 21007170 is about 4583.3579393279. The cubic root of 21007170 is about 275.9238132499.

Adding to 21007170 its reverse (7170012), we get a palindrome (28177182).

The spelling of 21007170 in words is "twenty-one million, seven thousand, one hundred seventy".