20121566 has 4 divisors (see below), whose sum is σ = 30182352. Its totient is φ = 10060782.

The previous prime is 20121559. The next prime is 20121581. The reversal of 20121566 is 66512102.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 66512102 = 2 ⋅33256051.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5030390 + ... + 5030393.

It is an arithmetic number, because the mean of its divisors is an integer number (7545588).

Almost surely, 2^20121566 is an apocalyptic number.

20121566 is a deficient number, since it is larger than the sum of its proper divisors (10060786).

20121566 is a wasteful number, since it uses less digits than its factorization.

20121566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10060785.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 20121566 is about 4485.7068562268. The cubic root of 20121566 is about 271.9906192699.

Adding to 20121566 its reverse (66512102), we get a palindrome (86633668).

The spelling of 20121566 in words is "twenty million, one hundred twenty-one thousand, five hundred sixty-six".