1251935921 has 4 divisors (see below), whose sum is σ = 1253177700. Its totient is φ = 1250694144.

The previous prime is 1251935873. The next prime is 1251935929. The reversal of 1251935921 is 1295391521.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1295391521 = 71 ⋅18244951.

It can be written as a sum of positive squares in 2 ways, for example, as 909685921 + 342250000 = 30161^2 + 18500^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1251935921 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1251935929) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 619376 + ... + 621393.

It is an arithmetic number, because the mean of its divisors is an integer number (313294425).

Almost surely, 2^1251935921 is an apocalyptic number.

It is an amenable number.

1251935921 is a deficient number, since it is larger than the sum of its proper divisors (1241779).

1251935921 is a wasteful number, since it uses less digits than its factorization.

1251935921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1241778.

The product of its digits is 24300, while the sum is 38.

The square root of 1251935921 is about 35382.7065245156. The cubic root of 1251935921 is about 1077.7731668886.

The spelling of 1251935921 in words is "one billion, two hundred fifty-one million, nine hundred thirty-five thousand, nine hundred twenty-one".