1661721523 has 8 divisors (see below), whose sum is σ = 2071756800. Its totient is φ = 1294847880.

The previous prime is 1661721521. The next prime is 1661721539. The reversal of 1661721523 is 3251271661.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1661721523 - 2¹ = 1661721521 is a prime.

It is a super-2 number, since 2×1661721523² = 5522636840002879058, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1661721521) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10790323 + ... + 10790476.

It is an arithmetic number, because the mean of its divisors is an integer number (258969600).

Almost surely, 2^1661721523 is an apocalyptic number.

1661721523 is a deficient number, since it is larger than the sum of its proper divisors (410035277).

1661721523 is a wasteful number, since it uses less digits than its factorization.

1661721523 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21580817.

The product of its digits is 15120, while the sum is 34.

The square root of 1661721523 is about 40764.2186604870. The cubic root of 1661721523 is about 1184.4573165966.

The spelling of 1661721523 in words is "one billion, six hundred sixty-one million, seven hundred twenty-one thousand, five hundred twenty-three".