21623755 has 4 divisors (see below), whose sum is σ = 25948512. Its totient is φ = 17299000.

The previous prime is 21623731. The next prime is 21623773. The reversal of 21623755 is 55732612.

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

It is not a de Polignac number, because 21623755 - 2⁷ = 21623627 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2162371 + ... + 2162380.

It is an arithmetic number, because the mean of its divisors is an integer number (6487128).

Almost surely, 2^21623755 is an apocalyptic number.

21623755 is a deficient number, since it is larger than the sum of its proper divisors (4324757).

21623755 is an equidigital number, since it uses as much as digits as its factorization.

21623755 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4324756.

The product of its digits is 12600, while the sum is 31.

The square root of 21623755 is about 4650.1349442785. The cubic root of 21623755 is about 278.5973860787.

The spelling of 21623755 in words is "twenty-one million, six hundred twenty-three thousand, seven hundred fifty-five".