661356 has 18 divisors (see below), whose sum is σ = 1671852. Its totient is φ = 220440.

The previous prime is 661343. The next prime is 661361. The reversal of 661356 is 653166.

661356 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (18).

It is an Ulam number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 9150 + ... + 9221.

2⁶⁶¹³⁵⁶ is an apocalyptic number.

It is an amenable number.

661356 is an abundant number, since it is smaller than the sum of its proper divisors (1010496).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

661356 is a wasteful number, since it uses less digits than its factorization.

661356 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18381 (or 18376 counting only the distinct ones).

The product of its digits is 3240, while the sum is 27.

The square root of 661356 is about 813.2379725517. The cubic root of 661356 is about 87.1254630568.

The spelling of 661356 in words is "six hundred sixty-one thousand, three hundred fifty-six".