21553251000 has 192 divisors, whose sum is σ = 68034077280. Its totient is φ = 5680665600.

The previous prime is 21553250977. The next prime is 21553251017. The reversal of 21553251000 is 15235512.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 94118886 + ... + 94119114.

Almost surely, 2^21553251000 is an apocalyptic number.

21553251000 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21553251000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34017038640).

21553251000 is an abundant number, since it is smaller than the sum of its proper divisors (46480826280).

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

21553251000 is a wasteful number, since it uses less digits than its factorization.

21553251000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 619 (or 376 counting only the distinct ones).

The product of its (nonzero) digits is 1500, while the sum is 24.

Adding to 21553251000 its reverse (15235512), we get a palindrome (21568486512).

The spelling of 21553251000 in words is "twenty-one billion, five hundred fifty-three million, two hundred fifty-one thousand".