1525215661 has 4 divisors (see below), whose sum is σ = 1525404672. Its totient is φ = 1525026652.

The previous prime is 1525215649. The next prime is 1525215683. The reversal of 1525215661 is 1665125251.

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: 1665125251 = 41 ⋅40612811.

It is a cyclic number.

It is not a de Polignac number, because 1525215661 - 2⁹ = 1525215149 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1525215611) 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, 81835 + ... + 98728.

It is an arithmetic number, because the mean of its divisors is an integer number (381351168).

Almost surely, 2^1525215661 is an apocalyptic number.

It is an amenable number.

1525215661 is a deficient number, since it is larger than the sum of its proper divisors (189011).

1525215661 is an equidigital number, since it uses as much as digits as its factorization.

1525215661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 189010.

The product of its digits is 18000, while the sum is 34.

The square root of 1525215661 is about 39054.0095380743. The cubic root of 1525215661 is about 1151.0930152590.

The spelling of 1525215661 in words is "one billion, five hundred twenty-five million, two hundred fifteen thousand, six hundred sixty-one".