661901405 has 16 divisors (see below), whose sum is σ = 878698368. Its totient is φ = 474600000.

The previous prime is 661901369. The next prime is 661901411. The reversal of 661901405 is 504109166.

It is not a de Polignac number, because 661901405 - 2¹² = 661897309 is a prime.

It is a super-2 number, since 2×661901405² = 876226939881948050, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

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, 80846 + ... + 88655.

It is an arithmetic number, because the mean of its divisors is an integer number (54918648).

Almost surely, 2^661901405 is an apocalyptic number.

It is an amenable number.

661901405 is a deficient number, since it is larger than the sum of its proper divisors (216796963).

661901405 is a wasteful number, since it uses less digits than its factorization.

661901405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 169588.

The product of its (nonzero) digits is 6480, while the sum is 32.

The square root of 661901405 is about 25727.4445874440. Note that the first 3 decimals coincide. The cubic root of 661901405 is about 871.4940659430.

The spelling of 661901405 in words is "six hundred sixty-one million, nine hundred one thousand, four hundred five".