20687561 has 8 divisors (see below), whose sum is σ = 21890880. Its totient is φ = 19495728.

The previous prime is 20687549. The next prime is 20687573. The reversal of 20687561 is 16578602.

It is an interprime number because it is at equal distance from previous prime (20687549) and next prime (20687573).

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 20687561 - 2⁶ = 20687497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20687581) 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, 980 + ... + 6506.

It is an arithmetic number, because the mean of its divisors is an integer number (2736360).

Almost surely, 2^20687561 is an apocalyptic number.

It is an amenable number.

20687561 is a deficient number, since it is larger than the sum of its proper divisors (1203319).

20687561 is a wasteful number, since it uses less digits than its factorization.

20687561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5743.

The product of its (nonzero) digits is 20160, while the sum is 35.

The square root of 20687561 is about 4548.3580553866. The cubic root of 20687561 is about 274.5173285323.

The spelling of 20687561 in words is "twenty million, six hundred eighty-seven thousand, five hundred sixty-one".