661021402400 has 36 divisors (see below), whose sum is σ = 1613718500562. Its totient is φ = 264408560640.

The previous prime is 661021402373. The next prime is 661021402423. The reversal of 661021402400 is 4204120166.

It can be written as a sum of positive squares in 3 ways, for example, as 476503045264 + 184518357136 = 690292^2 + 429556^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 661021402400.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 413137577 + ... + 413139176.

Almost surely, 2^661021402400 is an apocalyptic number.

It is an amenable number.

661021402400 is an abundant number, since it is smaller than the sum of its proper divisors (952697098162).

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

661021402400 is a wasteful number, since it uses less digits than its factorization.

661021402400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 826276773 (or 826276760 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 26.

Adding to 661021402400 its reverse (4204120166), we get a palindrome (665225522566).

The spelling of 661021402400 in words is "six hundred sixty-one billion, twenty-one million, four hundred two thousand, four hundred".