661491653 has 8 divisors (see below), whose sum is σ = 688504800. Its totient is φ = 634758768.

The previous prime is 661491643. The next prime is 661491659. The reversal of 661491653 is 356194166.

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 661491653 - 2¹² = 661487557 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 661491653.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661491659) 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, 65243 + ... + 74696.

It is an arithmetic number, because the mean of its divisors is an integer number (86063100).

Almost surely, 2^661491653 is an apocalyptic number.

It is an amenable number.

661491653 is a deficient number, since it is larger than the sum of its proper divisors (27013147).

661491653 is a wasteful number, since it uses less digits than its factorization.

661491653 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 140131.

The product of its digits is 116640, while the sum is 41.

The square root of 661491653 is about 25719.4800297362. The cubic root of 661491653 is about 871.3141951715.

The spelling of 661491653 in words is "six hundred sixty-one million, four hundred ninety-one thousand, six hundred fifty-three".