21209242500000 has 1920 divisors, whose sum is σ = 84740147908416. Its totient is φ = 5184000000000.

The previous prime is 21209242499999. The next prime is 21209242500059. The reversal of 21209242500000 is 524290212.

It is a happy number.

It can be written as a sum of positive squares in 32 ways, for example, as 18606144218256 + 2603098281744 = 4313484^2 + 1613412^2 .

It is a hoax number, since the sum of its digits (27) 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 (27).

It is an unprimeable number.

It is a polite number, since it can be written in 319 ways as a sum of consecutive naturals, for example, 209992499950 + ... + 209992500050.

Almost surely, 2^{21209242500000} is an apocalyptic number.

21209242500000 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 21209242500000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42370073954208).

21209242500000 is an abundant number, since it is smaller than the sum of its proper divisors (63530905408416).

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

21209242500000 is an frugal number, since it uses more digits than its factorization.

21209242500000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 236 (or 189 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 27.

Adding to 21209242500000 its reverse (524290212), we get a palindrome (21209766790212).

The spelling of 21209242500000 in words is "twenty-one trillion, two hundred nine billion, two hundred forty-two million, five hundred thousand".