661012401 has 12 divisors (see below), whose sum is σ = 1025243952. Its totient is φ = 377721288.

The previous prime is 661012381. The next prime is 661012403. The reversal of 661012401 is 104210166.

It is not a de Polignac number, because 661012401 - 2⁵ = 661012369 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is not an unprimeable number, because it can be changed into a prime (661012403) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2248195 + ... + 2248488.

It is an arithmetic number, because the mean of its divisors is an integer number (85436996).

Almost surely, 2^661012401 is an apocalyptic number.

It is an amenable number.

661012401 is a deficient number, since it is larger than the sum of its proper divisors (364231551).

661012401 is a wasteful number, since it uses less digits than its factorization.

661012401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4496700 (or 4496693 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 21.

The square root of 661012401 is about 25710.1614347324. The cubic root of 661012401 is about 871.1037213860.

Adding to 661012401 its reverse (104210166), we get a palindrome (765222567).

The spelling of 661012401 in words is "six hundred sixty-one million, twelve thousand, four hundred one".