20978351 has 4 divisors (see below), whose sum is σ = 21655104. Its totient is φ = 20301600.

The previous prime is 20978317. The next prime is 20978359. The reversal of 20978351 is 15387902.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 15387902 = 2 ⋅7693951.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20978351 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 (20978359) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 338330 + ... + 338391.

It is an arithmetic number, because the mean of its divisors is an integer number (5413776).

Almost surely, 2^20978351 is an apocalyptic number.

20978351 is a deficient number, since it is larger than the sum of its proper divisors (676753).

20978351 is an equidigital number, since it uses as much as digits as its factorization.

20978351 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 676752.

The product of its (nonzero) digits is 15120, while the sum is 35.

The square root of 20978351 is about 4580.2129863141. The cubic root of 20978351 is about 275.7975787717.

The spelling of 20978351 in words is "twenty million, nine hundred seventy-eight thousand, three hundred fifty-one".