21515441640 has 256 divisors, whose sum is σ = 80663869440. Its totient is φ = 4460160000.

The previous prime is 21515441579. The next prime is 21515441653. The reversal of 21515441640 is 4614451512.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 4257115 + ... + 4262165.

It is an arithmetic number, because the mean of its divisors is an integer number (315093240).

Almost surely, 2^21515441640 is an apocalyptic number.

21515441640 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 21515441640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40331934720).

21515441640 is an abundant number, since it is smaller than the sum of its proper divisors (59148427800).

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

21515441640 is a wasteful number, since it uses less digits than its factorization.

21515441640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5544 (or 5540 counting only the distinct ones).

The product of its (nonzero) digits is 19200, while the sum is 33.

The spelling of 21515441640 in words is "twenty-one billion, five hundred fifteen million, four hundred forty-one thousand, six hundred forty".