55440021 has 48 divisors (see below), whose sum is σ = 94202304. Its totient is φ = 28740096.

The previous prime is 55440013. The next prime is 55440031. The reversal of 55440021 is 12004455.

It is not a de Polignac number, because 55440021 - 2³ = 55440013 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 55440021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (55440031) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 127821 + ... + 128253.

It is an arithmetic number, because the mean of its divisors is an integer number (1962548).

Almost surely, 2^55440021 is an apocalyptic number.

It is an amenable number.

55440021 is a deficient number, since it is larger than the sum of its proper divisors (38762283).

55440021 is a wasteful number, since it uses less digits than its factorization.

55440021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 530 (or 523 counting only the distinct ones).

The product of its (nonzero) digits is 800, while the sum is 21.

The square root of 55440021 is about 7445.8055977846. The cubic root of 55440021 is about 381.3067225108.

Adding to 55440021 its reverse (12004455), we get a palindrome (67444476).

The spelling of 55440021 in words is "fifty-five million, four hundred forty thousand, twenty-one".