21515251512 has 64 divisors (see below), whose sum is σ = 55304040960. Its totient is φ = 6970924800.

The previous prime is 21515251507. The next prime is 21515251577.

21515251512 is nontrivially palindromic in base 10.

It is a super-2 number, since 2×21515251512² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21515251512.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 226323 + ... + 307005.

It is an arithmetic number, because the mean of its divisors is an integer number (864125640).

Almost surely, 2^21515251512 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21515251512, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27652020480).

21515251512 is an abundant number, since it is smaller than the sum of its proper divisors (33788789448).

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

21515251512 is a wasteful number, since it uses less digits than its factorization.

21515251512 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 81004 (or 81000 counting only the distinct ones).

The product of its digits is 5000, while the sum is 30.

The spelling of 21515251512 in words is "twenty-one billion, five hundred fifteen million, two hundred fifty-one thousand, five hundred twelve".