20616981 has 32 divisors (see below), whose sum is σ = 34560000. Its totient is φ = 10620480.

The previous prime is 20616979. The next prime is 20616983. The reversal of 20616981 is 18961602.

It is an interprime number because it is at equal distance from previous prime (20616979) and next prime (20616983).

It is not a de Polignac number, because 20616981 - 2¹ = 20616979 is a prime.

It is a super-2 number, since 2×20616981² = 850119811108722, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20616983) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 34120 + ... + 34718.

It is an arithmetic number, because the mean of its divisors is an integer number (1080000).

Almost surely, 2^20616981 is an apocalyptic number.

20616981 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

20616981 is a deficient number, since it is larger than the sum of its proper divisors (13943019).

20616981 is a wasteful number, since it uses less digits than its factorization.

20616981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 769.

The product of its (nonzero) digits is 5184, while the sum is 33.

The square root of 20616981 is about 4540.5925824720. The cubic root of 20616981 is about 274.2047814680.

The spelling of 20616981 in words is "twenty million, six hundred sixteen thousand, nine hundred eighty-one".