1660721551 has 8 divisors (see below), whose sum is σ = 1758777840. Its totient is φ = 1562706048.

The previous prime is 1660721549. The next prime is 1660721567. The reversal of 1660721551 is 1551270661.

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 1660721551 - 2¹ = 1660721549 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1660721591) 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, 124860 + ... + 137518.

It is an arithmetic number, because the mean of its divisors is an integer number (219847230).

Almost surely, 2^1660721551 is an apocalyptic number.

1660721551 is a deficient number, since it is larger than the sum of its proper divisors (98056289).

1660721551 is a wasteful number, since it uses less digits than its factorization.

1660721551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20393.

The product of its (nonzero) digits is 12600, while the sum is 34.

The square root of 1660721551 is about 40751.9514992841. The cubic root of 1660721551 is about 1184.2196791429.

The spelling of 1660721551 in words is "one billion, six hundred sixty million, seven hundred twenty-one thousand, five hundred fifty-one".