21210501540 has 96 divisors (see below), whose sum is σ = 60416133120. Its totient is φ = 5558515200.

The previous prime is 21210501509. The next prime is 21210501547. The reversal of 21210501540 is 4510501212.

It is not an unprimeable number, because it can be changed into a prime (21210501547) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 6253245 + ... + 6256635.

It is an arithmetic number, because the mean of its divisors is an integer number (629334720).

Almost surely, 2^21210501540 is an apocalyptic number.

21210501540 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 21210501540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30208066560).

21210501540 is an abundant number, since it is smaller than the sum of its proper divisors (39205631580).

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

21210501540 is a wasteful number, since it uses less digits than its factorization.

21210501540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5173 (or 5171 counting only the distinct ones).

The product of its (nonzero) digits is 400, while the sum is 21.

The spelling of 21210501540 in words is "twenty-one billion, two hundred ten million, five hundred one thousand, five hundred forty".