21023755 has 4 divisors (see below), whose sum is σ = 25228512. Its totient is φ = 16819000.

The previous prime is 21023741. The next prime is 21023759. The reversal of 21023755 is 55732012.

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

It is not a de Polignac number, because 21023755 - 2¹³ = 21015563 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21023759) 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, 2102371 + ... + 2102380.

It is an arithmetic number, because the mean of its divisors is an integer number (6307128).

Almost surely, 2^21023755 is an apocalyptic number.

21023755 is a deficient number, since it is larger than the sum of its proper divisors (4204757).

21023755 is an equidigital number, since it uses as much as digits as its factorization.

21023755 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4204756.

The product of its (nonzero) digits is 2100, while the sum is 25.

The square root of 21023755 is about 4585.1668453831. The cubic root of 21023755 is about 275.9964073957.

Adding to 21023755 its reverse (55732012), we get a palindrome (76755767).

The spelling of 21023755 in words is "twenty-one million, twenty-three thousand, seven hundred fifty-five".