21645011 has 4 divisors (see below), whose sum is σ = 21941592. Its totient is φ = 21348432.

The previous prime is 21644969. The next prime is 21645023. The reversal of 21645011 is 11054612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21645011 - 2⁶ = 21644947 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21645511) 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, 148181 + ... + 148326.

It is an arithmetic number, because the mean of its divisors is an integer number (5485398).

Almost surely, 2^21645011 is an apocalyptic number.

21645011 is a deficient number, since it is larger than the sum of its proper divisors (296581).

21645011 is an equidigital number, since it uses as much as digits as its factorization.

21645011 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 296580.

The product of its (nonzero) digits is 240, while the sum is 20.

The square root of 21645011 is about 4652.4199079619. The cubic root of 21645011 is about 278.6886426114.

Adding to 21645011 its reverse (11054612), we get a palindrome (32699623).

The spelling of 21645011 in words is "twenty-one million, six hundred forty-five thousand, eleven".