21020023 has 4 divisors (see below), whose sum is σ = 22126360. Its totient is φ = 19913688.

The previous prime is 21020017. The next prime is 21020029. The reversal of 21020023 is 32002012.

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

It is an interprime number because it is at equal distance from previous prime (21020017) and next prime (21020029).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21020023 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21019991 and 21020009.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21020029) 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, 553140 + ... + 553177.

It is an arithmetic number, because the mean of its divisors is an integer number (5531590).

Almost surely, 2^21020023 is an apocalyptic number.

21020023 is a deficient number, since it is larger than the sum of its proper divisors (1106337).

21020023 is a wasteful number, since it uses less digits than its factorization.

21020023 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1106336.

The product of its (nonzero) digits is 24, while the sum is 10.

The square root of 21020023 is about 4584.7598628500. The cubic root of 21020023 is about 275.9800754013.

Adding to 21020023 its reverse (32002012), we get a palindrome (53022035).

The spelling of 21020023 in words is "twenty-one million, twenty thousand, twenty-three".