19900661 has 16 divisors (see below), whose sum is σ = 22353408. Its totient is φ = 17564400.

The previous prime is 19900651. The next prime is 19900663. The reversal of 19900661 is 16600991.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 19900661 - 2¹⁸ = 19638517 is a prime.

19900661 is a strobogrammatic number because it is the same when read upside-down.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19900663) 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, 64670 + ... + 64976.

It is an arithmetic number, because the mean of its divisors is an integer number (1397088).

Almost surely, 2^19900661 is an apocalyptic number.

19900661 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

19900661 is a deficient number, since it is larger than the sum of its proper divisors (2452747).

19900661 is a wasteful number, since it uses less digits than its factorization.

19900661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 472.

The product of its (nonzero) digits is 2916, while the sum is 32.

The square root of 19900661 is about 4461.0156915214. The cubic root of 19900661 is about 270.9916029769.

The spelling of 19900661 in words is "nineteen million, nine hundred thousand, six hundred sixty-one".