21101023 has 4 divisors (see below), whose sum is σ = 21115080. Its totient is φ = 21086968.

The previous prime is 21100999. The next prime is 21101027. The reversal of 21101023 is 32010112.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21101023 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21101027) 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, 4465 + ... + 7882.

It is an arithmetic number, because the mean of its divisors is an integer number (5278770).

Almost surely, 2^21101023 is an apocalyptic number.

21101023 is a deficient number, since it is larger than the sum of its proper divisors (14057).

21101023 is a wasteful number, since it uses less digits than its factorization.

21101023 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14056.

The product of its (nonzero) digits is 12, while the sum is 10.

The square root of 21101023 is about 4593.5849834307. The cubic root of 21101023 is about 276.3341145547.

Adding to 21101023 its reverse (32010112), we get a palindrome (53111135).

The spelling of 21101023 in words is "twenty-one million, one hundred one thousand, twenty-three".