661561501616 has 30 divisors (see below), whose sum is σ = 1361609181420. Its totient is φ = 311323057408.

The previous prime is 661561501591. The next prime is 661561501681. The reversal of 661561501616 is 616105165166.

It is a super-2 number, since 2×661561501616² (a number of 24 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 71531006 + ... + 71540253.

It is an arithmetic number, because the mean of its divisors is an integer number (45386972714).

Almost surely, 2^661561501616 is an apocalyptic number.

It is an amenable number.

661561501616 is an abundant number, since it is smaller than the sum of its proper divisors (700047679804).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

661561501616 is a wasteful number, since it uses less digits than its factorization.

661561501616 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 143071301 (or 143071278 counting only the distinct ones).

The product of its (nonzero) digits is 194400, while the sum is 44.

The spelling of 661561501616 in words is "six hundred sixty-one billion, five hundred sixty-one million, five hundred one thousand, six hundred sixteen".