661126401 has 16 divisors (see below), whose sum is σ = 1054789120. Its totient is φ = 406846800.

The previous prime is 661126391. The next prime is 661126441. The reversal of 661126401 is 104621166.

661126401 is a `hidden beast` number, since 6 + 6 + 1 + 12 + 640 + 1 = 666.

It is not a de Polignac number, because 661126401 - 2⁹ = 661125889 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661126441) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 941425 + ... + 942126.

It is an arithmetic number, because the mean of its divisors is an integer number (65924320).

Almost surely, 2^661126401 is an apocalyptic number.

It is an amenable number.

661126401 is a deficient number, since it is larger than the sum of its proper divisors (393662719).

661126401 is a wasteful number, since it uses less digits than its factorization.

661126401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1883573 (or 1883567 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 661126401 is about 25712.3783614041. The cubic root of 661126401 is about 871.1537961479.

Adding to 661126401 its reverse (104621166), we get a palindrome (765747567).

The spelling of 661126401 in words is "six hundred sixty-one million, one hundred twenty-six thousand, four hundred one".