20749561 has 8 divisors (see below), whose sum is σ = 23959040. Its totient is φ = 17601408.

The previous prime is 20749543. The next prime is 20749601. The reversal of 20749561 is 16594702.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20749561 - 2⁷ = 20749433 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20749511) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 14601 + ... + 15958.

It is an arithmetic number, because the mean of its divisors is an integer number (2994880).

Almost surely, 2^20749561 is an apocalyptic number.

It is an amenable number.

20749561 is a deficient number, since it is larger than the sum of its proper divisors (3209479).

20749561 is an equidigital number, since it uses as much as digits as its factorization.

20749561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30663.

The product of its (nonzero) digits is 15120, while the sum is 34.

The square root of 20749561 is about 4555.1686028071. The cubic root of 20749561 is about 274.7912950918.

The spelling of 20749561 in words is "twenty million, seven hundred forty-nine thousand, five hundred sixty-one".