20681661 has 64 divisors (see below), whose sum is σ = 37933056. Its totient is φ = 9676800.

The previous prime is 20681659. The next prime is 20681663. The reversal of 20681661 is 16618602.

It is an interprime number because it is at equal distance from previous prime (20681659) and next prime (20681663).

It is not a de Polignac number, because 20681661 - 2¹ = 20681659 is a prime.

It is a super-2 number, since 2×20681661² = 855462203437842, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20681663) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 213165 + ... + 213261.

It is an arithmetic number, because the mean of its divisors is an integer number (592704).

Almost surely, 2^20681661 is an apocalyptic number.

20681661 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

20681661 is a deficient number, since it is larger than the sum of its proper divisors (17251395).

20681661 is a wasteful number, since it uses less digits than its factorization.

20681661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 202.

The product of its (nonzero) digits is 3456, while the sum is 30.

The square root of 20681661 is about 4547.7094234351. The cubic root of 20681661 is about 274.4912290123.

The spelling of 20681661 in words is "twenty million, six hundred eighty-one thousand, six hundred sixty-one".