20428639 has 24 divisors (see below), whose sum is σ = 26199936. Its totient is φ = 15750000.

The previous prime is 20428637. The next prime is 20428643. The reversal of 20428639 is 93682402.

It is not a de Polignac number, because 20428639 - 2¹ = 20428637 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20428631) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 81264 + ... + 81514.

It is an arithmetic number, because the mean of its divisors is an integer number (1091664).

Almost surely, 2^20428639 is an apocalyptic number.

20428639 is a deficient number, since it is larger than the sum of its proper divisors (5771297).

20428639 is a wasteful number, since it uses less digits than its factorization.

20428639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 427 (or 420 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 34.

The square root of 20428639 is about 4519.8051949171. The cubic root of 20428639 is about 273.3672462714.

The spelling of 20428639 in words is "twenty million, four hundred twenty-eight thousand, six hundred thirty-nine".