21995550 has 60 divisors (see below), whose sum is σ = 61126296. Its totient is φ = 5864400.

The previous prime is 21995537. The next prime is 21995551. The reversal of 21995550 is 5559912.

21995550 is a `hidden beast` number, since 2 + 19 + 95 + 550 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21995551) by changing a digit.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 1335 + ... + 6765.

Almost surely, 2^21995550 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21995550, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30563148).

21995550 is an abundant number, since it is smaller than the sum of its proper divisors (39130746).

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

21995550 is a wasteful number, since it uses less digits than its factorization.

21995550 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5455 (or 5441 counting only the distinct ones).

The product of its (nonzero) digits is 20250, while the sum is 36.

The square root of 21995550 is about 4689.9413642390. The cubic root of 21995550 is about 280.1850392537.

The spelling of 21995550 in words is "twenty-one million, nine hundred ninety-five thousand, five hundred fifty".