21515506012 has 192 divisors, whose sum is σ = 51750171648. Its totient is φ = 7557120000.

The previous prime is 21515505959. The next prime is 21515506013. The reversal of 21515506012 is 21060551512.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21515506013) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 33565212 + ... + 33565852.

It is an arithmetic number, because the mean of its divisors is an integer number (269532144).

Almost surely, 2^21515506012 is an apocalyptic number.

21515506012 is a gapful number since it is divisible by the number (22) 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 21515506012, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25875085824).

21515506012 is an abundant number, since it is smaller than the sum of its proper divisors (30234665636).

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

21515506012 is a wasteful number, since it uses less digits than its factorization.

21515506012 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 860 (or 858 counting only the distinct ones).

The product of its (nonzero) digits is 3000, while the sum is 28.

The spelling of 21515506012 in words is "twenty-one billion, five hundred fifteen million, five hundred six thousand, twelve".