1521393661 has 4 divisors (see below), whose sum is σ = 1521589212. Its totient is φ = 1521198112.

The previous prime is 1521393649. The next prime is 1521393677. The reversal of 1521393661 is 1663931251.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1211457636 + 309936025 = 34806^2 + 17605^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1521393661 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1521393661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1521393611) 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, 85600 + ... + 101833.

It is an arithmetic number, because the mean of its divisors is an integer number (380397303).

Almost surely, 2^1521393661 is an apocalyptic number.

It is an amenable number.

1521393661 is a deficient number, since it is larger than the sum of its proper divisors (195551).

1521393661 is an equidigital number, since it uses as much as digits as its factorization.

1521393661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 195550.

The product of its digits is 29160, while the sum is 37.

The square root of 1521393661 is about 39005.0466093812. The cubic root of 1521393661 is about 1150.1307125525.

The spelling of 1521393661 in words is "one billion, five hundred twenty-one million, three hundred ninety-three thousand, six hundred sixty-one".