1251998640 has 80 divisors (see below), whose sum is σ = 4312447200. Its totient is φ = 333865728.

The previous prime is 1251998633. The next prime is 1251998641. The reversal of 1251998640 is 468991521.

1251998640 is a `hidden beast` number, since 1 + 2 + 519 + 98 + 6 + 40 = 666.

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

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (1251998641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 287655 + ... + 291974.

It is an arithmetic number, because the mean of its divisors is an integer number (53905590).

Almost surely, 2^1251998640 is an apocalyptic number.

1251998640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1251998640 is an abundant number, since it is smaller than the sum of its proper divisors (3060448560).

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

1251998640 is a wasteful number, since it uses less digits than its factorization.

1251998640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 579651 (or 579639 counting only the distinct ones).

The product of its (nonzero) digits is 155520, while the sum is 45.

The square root of 1251998640 is about 35383.5928079668. The cubic root of 1251998640 is about 1077.7911645421.

The spelling of 1251998640 in words is "one billion, two hundred fifty-one million, nine hundred ninety-eight thousand, six hundred forty".