21115131500 has 24 divisors (see below), whose sum is σ = 46115448288. Its totient is φ = 8446052400.

The previous prime is 21115131493. The next prime is 21115131559. The reversal of 21115131500 is 513151112.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 21114632 + ... + 21115631.

It is an arithmetic number, because the mean of its divisors is an integer number (1921477012).

Almost surely, 2^21115131500 is an apocalyptic number.

21115131500 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21115131500 is an abundant number, since it is smaller than the sum of its proper divisors (25000316788).

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

21115131500 is a wasteful number, since it uses less digits than its factorization.

21115131500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42230282 (or 42230270 counting only the distinct ones).

The product of its (nonzero) digits is 150, while the sum is 20.

Adding to 21115131500 its reverse (513151112), we get a palindrome (21628282612).

The spelling of 21115131500 in words is "twenty-one billion, one hundred fifteen million, one hundred thirty-one thousand, five hundred".