20210661 has 16 divisors (see below), whose sum is σ = 31518400. Its totient is φ = 12764304.

The previous prime is 20210657. The next prime is 20210669. The reversal of 20210661 is 16601202.

It is a happy number.

20210661 is a `hidden beast` number, since 2 + 0 + 2 + 1 + 0 + 661 = 666.

It is not a de Polignac number, because 20210661 - 2² = 20210657 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20210669) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19186 + ... + 20211.

It is an arithmetic number, because the mean of its divisors is an integer number (1969900).

Almost surely, 2^20210661 is an apocalyptic number.

It is an amenable number.

20210661 is a deficient number, since it is larger than the sum of its proper divisors (11307739).

20210661 is a wasteful number, since it uses less digits than its factorization.

20210661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39425 (or 39419 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

The square root of 20210661 is about 4495.6268750865. The cubic root of 20210661 is about 272.3914715256.

Adding to 20210661 its reverse (16601202), we get a palindrome (36811863).

It can be divided in two parts, 20 and 210661, that added together give a square (210681 = 459²).

The spelling of 20210661 in words is "twenty million, two hundred ten thousand, six hundred sixty-one".