661021207 has 16 divisors (see below), whose sum is σ = 841669632. Its totient is φ = 504119520.

The previous prime is 661021199. The next prime is 661021211. The reversal of 661021207 is 702120166.

661021207 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is not a de Polignac number, because 661021207 - 2³ = 661021199 is a prime.

It is a super-2 number, since 2×661021207² = 873898072207473698, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661021607) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 87708 + ... + 94945.

It is an arithmetic number, because the mean of its divisors is an integer number (52604352).

Almost surely, 2^661021207 is an apocalyptic number.

661021207 is a deficient number, since it is larger than the sum of its proper divisors (180648425).

661021207 is a wasteful number, since it uses less digits than its factorization.

661021207 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 182718.

The product of its (nonzero) digits is 1008, while the sum is 25.

The square root of 661021207 is about 25710.3326894072. The cubic root of 661021207 is about 871.1075896469.

The spelling of 661021207 in words is "six hundred sixty-one million, twenty-one thousand, two hundred seven".