20487778 has 4 divisors (see below), whose sum is σ = 30731670. Its totient is φ = 10243888.

The previous prime is 20487773. The next prime is 20487787. The reversal of 20487778 is 87778402.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 87778402 = 2 ⋅43889201.

It can be written as a sum of positive squares in only one way, i.e., 17164449 + 3323329 = 4143^2 + 1823^2 .

It is not an unprimeable number, because it can be changed into a prime (20487773) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5121943 + ... + 5121946.

Almost surely, 2^20487778 is an apocalyptic number.

20487778 is a deficient number, since it is larger than the sum of its proper divisors (10243892).

20487778 is a wasteful number, since it uses less digits than its factorization.

20487778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10243891.

The product of its (nonzero) digits is 175616, while the sum is 43.

The square root of 20487778 is about 4526.3426737268. The cubic root of 20487778 is about 273.6307830035.

The spelling of 20487778 in words is "twenty million, four hundred eighty-seven thousand, seven hundred seventy-eight".