20978831 has 16 divisors (see below), whose sum is σ = 22861440. Its totient is φ = 19188000.

The previous prime is 20978819. The next prime is 20978843. The reversal of 20978831 is 13887902.

It is an interprime number because it is at equal distance from previous prime (20978819) and next prime (20978843).

It is a cyclic number.

It is not a de Polignac number, because 20978831 - 2⁶ = 20978767 is a prime.

It is a super-2 number, since 2×20978831² = 880222700253122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20978431) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 83456 + ... + 83706.

It is an arithmetic number, because the mean of its divisors is an integer number (1428840).

Almost surely, 2^20978831 is an apocalyptic number.

20978831 is a deficient number, since it is larger than the sum of its proper divisors (1882609).

20978831 is a wasteful number, since it uses less digits than its factorization.

20978831 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 406.

The product of its (nonzero) digits is 24192, while the sum is 38.

The square root of 20978831 is about 4580.2653853243. The cubic root of 20978831 is about 275.7996822390.

The spelling of 20978831 in words is "twenty million, nine hundred seventy-eight thousand, eight hundred thirty-one".