20821678 has 4 divisors (see below), whose sum is σ = 31232520. Its totient is φ = 10410838.

The previous prime is 20821667. The next prime is 20821709. The reversal of 20821678 is 87612802.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 87612802 = 2 ⋅43806401.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5205418 + ... + 5205421.

It is an arithmetic number, because the mean of its divisors is an integer number (7808130).

Almost surely, 2^20821678 is an apocalyptic number.

20821678 is a deficient number, since it is larger than the sum of its proper divisors (10410842).

20821678 is a wasteful number, since it uses less digits than its factorization.

20821678 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10410841.

The product of its (nonzero) digits is 10752, while the sum is 34.

The square root of 20821678 is about 4563.0776894548. The cubic root of 20821678 is about 275.1092810854.

Subtracting from 20821678 its product of nonzero digits (10752), we obtain a triangular number (20810926 = T₆₄₅₁).

The spelling of 20821678 in words is "twenty million, eight hundred twenty-one thousand, six hundred seventy-eight".