1525993981 has 4 divisors (see below), whose sum is σ = 1527371100. Its totient is φ = 1524616864.

The previous prime is 1525993957. The next prime is 1525993993. The reversal of 1525993981 is 1893995251.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1893995251 = 31 ⋅61096621.

It can be written as a sum of positive squares in 2 ways, for example, as 176092900 + 1349901081 = 13270^2 + 36741^2 .

It is a cyclic number.

It is not a de Polignac number, because 1525993981 - 2⁷ = 1525993853 is a prime.

It is a super-2 number, since 2×1525993981² = 4657315260096456722, 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 (1525993901) 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, 686896 + ... + 689113.

It is an arithmetic number, because the mean of its divisors is an integer number (381842775).

Almost surely, 2^1525993981 is an apocalyptic number.

It is an amenable number.

1525993981 is a deficient number, since it is larger than the sum of its proper divisors (1377119).

1525993981 is a wasteful number, since it uses less digits than its factorization.

1525993981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1377118.

The product of its digits is 874800, while the sum is 52.

The square root of 1525993981 is about 39063.9729290301. The cubic root of 1525993981 is about 1151.2887835003.

The spelling of 1525993981 in words is "one billion, five hundred twenty-five million, nine hundred ninety-three thousand, nine hundred eighty-one".