20400661 has 8 divisors (see below), whose sum is σ = 21525920. Its totient is φ = 19280592.

The previous prime is 20400637. The next prime is 20400671. The reversal of 20400661 is 16600402.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20400661 - 2²³ = 12012053 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (19).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20400631) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8911 + ... + 10963.

It is an arithmetic number, because the mean of its divisors is an integer number (2690740).

Almost surely, 2^20400661 is an apocalyptic number.

It is an amenable number.

20400661 is a deficient number, since it is larger than the sum of its proper divisors (1125259).

20400661 is a wasteful number, since it uses less digits than its factorization.

20400661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2595.

The product of its (nonzero) digits is 288, while the sum is 19.

The square root of 20400661 is about 4516.7090895917. The cubic root of 20400661 is about 273.2423927421.

The spelling of 20400661 in words is "twenty million, four hundred thousand, six hundred sixty-one".