21257735240 has 64 divisors (see below), whose sum is σ = 54736853760. Its totient is φ = 7278485760.

The previous prime is 21257735203. The next prime is 21257735251. The reversal of 21257735240 is 4253775212.

It is a junction number, because it is equal to n+sod(n) for n = 21257735194 and 21257735203.

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, 156950 + ... + 259130.

It is an arithmetic number, because the mean of its divisors is an integer number (855263340).

Almost surely, 2^21257735240 is an apocalyptic number.

21257735240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21257735240 is an abundant number, since it is smaller than the sum of its proper divisors (33479118520).

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

21257735240 is a wasteful number, since it uses less digits than its factorization.

21257735240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 102942 (or 102938 counting only the distinct ones).

The product of its (nonzero) digits is 117600, while the sum is 38.

The spelling of 21257735240 in words is "twenty-one billion, two hundred fifty-seven million, seven hundred thirty-five thousand, two hundred forty".