55215440 has 80 divisors (see below), whose sum is σ = 150192768. Its totient is φ = 18482688.

The previous prime is 55215427. The next prime is 55215451. The reversal of 55215440 is 4451255.

55215440 = T₁₅₈₁ + T₁₅₈₂ + ... + T₁₆₂₃.

It is a tau number, because it is divible by the number of its divisors (80).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 22934 + ... + 25226.

Almost surely, 2^55215440 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 55215440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (75096384).

55215440 is an abundant number, since it is smaller than the sum of its proper divisors (94977328).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

55215440 is a wasteful number, since it uses less digits than its factorization.

55215440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2356 (or 2350 counting only the distinct ones).

The product of its (nonzero) digits is 4000, while the sum is 26.

The square root of 55215440 is about 7430.7092528237. The cubic root of 55215440 is about 380.7911494895.

Adding to 55215440 its reverse (4451255), we get a palindrome (59666695).

It can be divided in two parts, 55215 and 440, that added together give a palindrome (55655).

The spelling of 55215440 in words is "fifty-five million, two hundred fifteen thousand, four hundred forty".