661681620004 has 24 divisors (see below), whose sum is σ = 1180453176000. Its totient is φ = 324416293344.

The previous prime is 661681619957. The next prime is 661681620031. The reversal of 661681620004 is 400026186166.

It is a happy number.

It is a super-2 number, since 2×661681620004² (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 7 ways as a sum of consecutive naturals, for example, 497254 + ... + 1253245.

It is an arithmetic number, because the mean of its divisors is an integer number (49185549000).

Almost surely, 2^661681620004 is an apocalyptic number.

It is an amenable number.

661681620004 is a deficient number, since it is larger than the sum of its proper divisors (518771555996).

661681620004 is a wasteful number, since it uses less digits than its factorization.

661681620004 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1752339 (or 1752337 counting only the distinct ones).

The product of its (nonzero) digits is 82944, while the sum is 40.

The spelling of 661681620004 in words is "six hundred sixty-one billion, six hundred eighty-one million, six hundred twenty thousand, four".