20787551 has 4 divisors (see below), whose sum is σ = 20854704. Its totient is φ = 20720400.

The previous prime is 20787541. The next prime is 20787581. The reversal of 20787551 is 15578702.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20787551 - 2¹⁰ = 20786527 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 (20787511) 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, 33110 + ... + 33731.

It is an arithmetic number, because the mean of its divisors is an integer number (5213676).

Almost surely, 2^20787551 is an apocalyptic number.

20787551 is a deficient number, since it is larger than the sum of its proper divisors (67153).

20787551 is an equidigital number, since it uses as much as digits as its factorization.

20787551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67152.

The product of its (nonzero) digits is 19600, while the sum is 35.

The square root of 20787551 is about 4559.3366842119. The cubic root of 20787551 is about 274.9588963360.

The spelling of 20787551 in words is "twenty million, seven hundred eighty-seven thousand, five hundred fifty-one".