1251681920 has 64 divisors (see below), whose sum is σ = 3048843240. Its totient is φ = 491212800.

The previous prime is 1251681911. The next prime is 1251681929. The reversal of 1251681920 is 291861521.

It is an interprime number because it is at equal distance from previous prime (1251681911) and next prime (1251681929).

It can be written as a sum of positive squares in 4 ways, for example, as 766625344 + 485056576 = 27688^2 + 22024^2 .

It is a tau number, because it is divible by the number of its divisors (64).

It is not an unprimeable number, because it can be changed into a prime (1251681929) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15470 + ... + 52370.

Almost surely, 2^1251681920 is an apocalyptic number.

1251681920 is a gapful number since it is divisible by the number (10) 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 1251681920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1524421620).

1251681920 is an abundant number, since it is smaller than the sum of its proper divisors (1797161320).

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

1251681920 is an equidigital number, since it uses as much as digits as its factorization.

1251681920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36973 (or 36961 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 35.

The square root of 1251681920 is about 35379.1170042442. The cubic root of 1251681920 is about 1077.7002733873.

The spelling of 1251681920 in words is "one billion, two hundred fifty-one million, six hundred eighty-one thousand, nine hundred twenty".