21097556550 has 576 divisors, whose sum is σ = 70780469760. Its totient is φ = 4402944000.

The previous prime is 21097556527. The next prime is 21097556561. The reversal of 21097556550 is 5565579012.

21097556550 is a `hidden beast` number, since 2 + 1 + 0 + 97 + 5 + 5 + 6 + 550 = 666.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21097556496 and 21097556505.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 287 ways as a sum of consecutive naturals, for example, 161049985 + ... + 161050115.

It is an arithmetic number, because the mean of its divisors is an integer number (122882760).

Almost surely, 2^21097556550 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21097556550, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35390234880).

21097556550 is an abundant number, since it is smaller than the sum of its proper divisors (49682913210).

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

21097556550 is a wasteful number, since it uses less digits than its factorization.

21097556550 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 269 (or 261 counting only the distinct ones).

The product of its (nonzero) digits is 472500, while the sum is 45.

The spelling of 21097556550 in words is "twenty-one billion, ninety-seven million, five hundred fifty-six thousand, five hundred fifty".