21653370 has 48 divisors (see below), whose sum is σ = 57507840. Its totient is φ = 5650272.

The previous prime is 21653363. The next prime is 21653377. The reversal of 21653370 is 7335612.

It is a happy number.

21653370 is a `hidden beast` number, since 2 + 1 + 653 + 3 + 7 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (21653363) and next prime (21653377).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21653377) 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, 1671 + ... + 6789.

It is an arithmetic number, because the mean of its divisors is an integer number (1198080).

Almost surely, 2^21653370 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21653370, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28753920).

21653370 is an abundant number, since it is smaller than the sum of its proper divisors (35854470).

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

21653370 is a wasteful number, since it uses less digits than its factorization.

21653370 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5179 (or 5176 counting only the distinct ones).

The product of its (nonzero) digits is 3780, while the sum is 27.

The square root of 21653370 is about 4653.3181709400. The cubic root of 21653370 is about 278.7245132107.

Adding to 21653370 its reverse (7335612), we get a palindrome (28988982).

The spelling of 21653370 in words is "twenty-one million, six hundred fifty-three thousand, three hundred seventy".