1661406401 has 2 divisors, whose sum is σ = 1661406402. Its totient is φ = 1661406400.

The previous prime is 1661406391. The next prime is 1661406427. The reversal of 1661406401 is 1046041661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1622156176 + 39250225 = 40276^2 + 6265^2 .

It is a cyclic number.

It is not a de Polignac number, because 1661406401 - 2¹⁰ = 1661405377 is a prime.

It is not a weakly prime, because it can be changed into another prime (1661406101) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830703200 + 830703201.

It is an arithmetic number, because the mean of its divisors is an integer number (830703201).

Almost surely, 2^1661406401 is an apocalyptic number.

It is an amenable number.

1661406401 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661406401 is an equidigital number, since it uses as much as digits as its factorization.

1661406401 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3456, while the sum is 29.

The square root of 1661406401 is about 40760.3532982726. The cubic root of 1661406401 is about 1184.3824400003.

The spelling of 1661406401 in words is "one billion, six hundred sixty-one million, four hundred six thousand, four hundred one".