20973661 has 4 divisors (see below), whose sum is σ = 21051900. Its totient is φ = 20895424.

The previous prime is 20973653. The next prime is 20973679. The reversal of 20973661 is 16637902.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16637902 = 2 ⋅8318951.

It can be written as a sum of positive squares in 2 ways, for example, as 6579225 + 14394436 = 2565^2 + 3794^2 .

It is a cyclic number.

It is not a de Polignac number, because 20973661 - 2³ = 20973653 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20971661) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 38716 + ... + 39253.

It is an arithmetic number, because the mean of its divisors is an integer number (5262975).

Almost surely, 2^20973661 is an apocalyptic number.

It is an amenable number.

20973661 is a deficient number, since it is larger than the sum of its proper divisors (78239).

20973661 is an equidigital number, since it uses as much as digits as its factorization.

20973661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 78238.

The product of its (nonzero) digits is 13608, while the sum is 34.

The square root of 20973661 is about 4579.7009727710. The cubic root of 20973661 is about 275.7770244544. Note that the first 3 decimals are identical.

The spelling of 20973661 in words is "twenty million, nine hundred seventy-three thousand, six hundred sixty-one".