21645370 has 32 divisors (see below), whose sum is σ = 42134400. Its totient is φ = 7978176.

The previous prime is 21645343. The next prime is 21645373. The reversal of 21645370 is 7354612.

It is not an unprimeable number, because it can be changed into a prime (21645373) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5491 + ... + 8569.

It is an arithmetic number, because the mean of its divisors is an integer number (1316700).

Almost surely, 2^21645370 is an apocalyptic number.

21645370 is a deficient number, since it is larger than the sum of its proper divisors (20489030).

21645370 is a wasteful number, since it uses less digits than its factorization.

21645370 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3142.

The product of its (nonzero) digits is 5040, while the sum is 28.

The square root of 21645370 is about 4652.4584898739. The cubic root of 21645370 is about 278.6901833617.

Adding to 21645370 its reverse (7354612), we get a palindrome (28999982).

The spelling of 21645370 in words is "twenty-one million, six hundred forty-five thousand, three hundred seventy".