21010505240 has 32 divisors (see below), whose sum is σ = 47279700000. Its totient is φ = 8403124224.

The previous prime is 21010505213. The next prime is 21010505297. The reversal of 21010505240 is 4250501012.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 330776 + ... + 389144.

It is an arithmetic number, because the mean of its divisors is an integer number (1477490625).

Almost surely, 2^21010505240 is an apocalyptic number.

21010505240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21010505240 is an abundant number, since it is smaller than the sum of its proper divisors (26269194760).

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

21010505240 is a wasteful number, since it uses less digits than its factorization.

21010505240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 67379 (or 67375 counting only the distinct ones).

The product of its (nonzero) digits is 400, while the sum is 20.

The spelling of 21010505240 in words is "twenty-one billion, ten million, five hundred five thousand, two hundred forty".