1661521653 has 20 divisors (see below), whose sum is σ = 2707666368. Its totient is φ = 1006982280.

The previous prime is 1661521651. The next prime is 1661521681. The reversal of 1661521653 is 3561251661.

1661521653 is a `hidden beast` number, since 16 + 61 + 521 + 65 + 3 = 666.

It is not a de Polignac number, because 1661521653 - 2¹ = 1661521651 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661521651) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 931501 + ... + 933282.

Almost surely, 2^1661521653 is an apocalyptic number.

It is an amenable number.

1661521653 is a deficient number, since it is larger than the sum of its proper divisors (1046144715).

1661521653 is a wasteful number, since it uses less digits than its factorization.

1661521653 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1864806 (or 1864797 counting only the distinct ones).

The product of its digits is 32400, while the sum is 36.

The square root of 1661521653 is about 40761.7670495282. The cubic root of 1661521653 is about 1184.4098262936.

The spelling of 1661521653 in words is "one billion, six hundred sixty-one million, five hundred twenty-one thousand, six hundred fifty-three".