21440057 has 8 divisors (see below), whose sum is σ = 22173000. Its totient is φ = 20715264.

The previous prime is 21440051. The next prime is 21440059. The reversal of 21440057 is 75004412.

It can be written as a sum of positive squares in 4 ways, for example, as 5271616 + 16168441 = 2296^2 + 4021^2 .

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

It is not a de Polignac number, because 21440057 - 2⁸ = 21439801 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21440051) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3569 + ... + 7457.

It is an arithmetic number, because the mean of its divisors is an integer number (2771625).

Almost surely, 2^21440057 is an apocalyptic number.

It is an amenable number.

21440057 is a deficient number, since it is larger than the sum of its proper divisors (732943).

21440057 is a wasteful number, since it uses less digits than its factorization.

21440057 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4075.

The product of its (nonzero) digits is 1120, while the sum is 23.

The square root of 21440057 is about 4630.3409161745. The cubic root of 21440057 is about 277.8062285111.

Adding to 21440057 its reverse (75004412), we get a palindrome (96444469).

The spelling of 21440057 in words is "twenty-one million, four hundred forty thousand, fifty-seven".