1915927981 has 4 divisors (see below), whose sum is σ = 2090103264. Its totient is φ = 1741752700.

The previous prime is 1915927963. The next prime is 1915928057. The reversal of 1915927981 is 1897295191.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1897295191 = 11 ⋅172481381.

It is a cyclic number.

It is not a de Polignac number, because 1915927981 - 2²³ = 1907539373 is a prime.

It is a super-2 number, since 2×1915927981² = 7341560056757472722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1915927381) 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, 87087625 + ... + 87087646.

It is an arithmetic number, because the mean of its divisors is an integer number (522525816).

Almost surely, 2^1915927981 is an apocalyptic number.

1915927981 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1915927981 is a deficient number, since it is larger than the sum of its proper divisors (174175283).

1915927981 is a wasteful number, since it uses less digits than its factorization.

1915927981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 174175282.

The product of its digits is 408240, while the sum is 52.

The square root of 1915927981 is about 43771.3145907225. The cubic root of 1915927981 is about 1242.0137200787.

The spelling of 1915927981 in words is "one billion, nine hundred fifteen million, nine hundred twenty-seven thousand, nine hundred eighty-one".