405001661 has 2 divisors, whose sum is σ = 405001662. Its totient is φ = 405001660.

The previous prime is 405001657. The next prime is 405001691. The reversal of 405001661 is 166100504.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 214036900 + 190964761 = 14630^2 + 13819^2 .

It is a cyclic number.

It is not a de Polignac number, because 405001661 - 2² = 405001657 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (405001651) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 202500830 + 202500831.

It is an arithmetic number, because the mean of its divisors is an integer number (202500831).

Almost surely, 2^405001661 is an apocalyptic number.

It is an amenable number.

405001661 is a deficient number, since it is larger than the sum of its proper divisors (1).

405001661 is an equidigital number, since it uses as much as digits as its factorization.

405001661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 405001661 is about 20124.6530653326. The cubic root of 405001661 is about 739.8646337492.

The spelling of 405001661 in words is "four hundred five million, one thousand, six hundred sixty-one".