251220040240 has 80 divisors (see below), whose sum is σ = 631066046688. Its totient is φ = 92455907328.

The previous prime is 251220040219. The next prime is 251220040243. The reversal of 251220040240 is 42040022152.

It is a tau number, because it is divible by the number of its divisors (80).

It is a super-2 number, since 2×251220040240² (a number of 24 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (251220040243) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 74137 + ... + 712696.

Almost surely, 2^251220040240 is an apocalyptic number.

251220040240 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 251220040240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (315533023344).

251220040240 is an abundant number, since it is smaller than the sum of its proper divisors (379846006448).

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

251220040240 is a wasteful number, since it uses less digits than its factorization.

251220040240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 787166 (or 787160 counting only the distinct ones).

The product of its (nonzero) digits is 1280, while the sum is 22.

Adding to 251220040240 its reverse (42040022152), we get a palindrome (293260062392).

The spelling of 251220040240 in words is "two hundred fifty-one billion, two hundred twenty million, forty thousand, two hundred forty".