21957805 has 8 divisors (see below), whose sum is σ = 26398944. Its totient is φ = 17533200.

The previous prime is 21957799. The next prime is 21957809. The reversal of 21957805 is 50875912.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21957805 - 2²³ = 13569197 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 (21957809) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 991 + ... + 6700.

It is an arithmetic number, because the mean of its divisors is an integer number (3299868).

Almost surely, 2^21957805 is an apocalyptic number.

It is an amenable number.

21957805 is a deficient number, since it is larger than the sum of its proper divisors (4441139).

21957805 is an equidigital number, since it uses as much as digits as its factorization.

21957805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8267.

The product of its (nonzero) digits is 25200, while the sum is 37.

The square root of 21957805 is about 4685.9155988985. The cubic root of 21957805 is about 280.0246789472.

It can be divided in two parts, 2195 and 7805, that added together give a 4-th power (10000 = 10⁴).

The spelling of 21957805 in words is "twenty-one million, nine hundred fifty-seven thousand, eight hundred five".