20978631 has 6 divisors (see below), whose sum is σ = 30302480. Its totient is φ = 13985748.

The previous prime is 20978623. The next prime is 20978669. The reversal of 20978631 is 13687902.

It is not a de Polignac number, because 20978631 - 2³ = 20978623 is a prime.

It is a super-2 number, since 2×20978631² = 880205917268322, which contains 22 as substring.

It is a Duffinian number.

It is a plaindrome in base 13.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20978611) 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 5 ways as a sum of consecutive naturals, for example, 1165471 + ... + 1165488.

Almost surely, 2^20978631 is an apocalyptic number.

20978631 is a deficient number, since it is larger than the sum of its proper divisors (9323849).

20978631 is a wasteful number, since it uses less digits than its factorization.

20978631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2330965 (or 2330962 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 20978631 is about 4580.2435524762. The cubic root of 20978631 is about 275.7988057982.

It can be divided in two parts, 20978 and 631, that added together give a square (21609 = 147²).

The spelling of 20978631 in words is "twenty million, nine hundred seventy-eight thousand, six hundred thirty-one".