55721550 has 96 divisors (see below), whose sum is σ = 144955008. Its totient is φ = 14152320.

The previous prime is 55721537. The next prime is 55721551. The reversal of 55721550 is 5512755.

It is a super-2 number, since 2×55721550² = 6209782268805000, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (55721551) 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, 341769 + ... + 341931.

It is an arithmetic number, because the mean of its divisors is an integer number (1509948).

Almost surely, 2^55721550 is an apocalyptic number.

55721550 is a gapful number since it is divisible by the number (50) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 55721550, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (72477504).

55721550 is an abundant number, since it is smaller than the sum of its proper divisors (89233458).

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

55721550 is a wasteful number, since it uses less digits than its factorization.

55721550 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 274 (or 269 counting only the distinct ones).

The product of its (nonzero) digits is 8750, while the sum is 30.

The square root of 55721550 is about 7464.6868655021. The cubic root of 55721550 is about 381.9510687214.

The spelling of 55721550 in words is "fifty-five million, seven hundred twenty-one thousand, five hundred fifty".