1216021541 has 4 divisors (see below), whose sum is σ = 1389738912. Its totient is φ = 1042304172.

The previous prime is 1216021537. The next prime is 1216021561. The reversal of 1216021541 is 1451206121.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 1216021541 - 2² = 1216021537 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1216021561) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 86858675 + ... + 86858688.

It is an arithmetic number, because the mean of its divisors is an integer number (347434728).

Almost surely, 2^1216021541 is an apocalyptic number.

It is an amenable number.

1216021541 is a deficient number, since it is larger than the sum of its proper divisors (173717371).

1216021541 is an equidigital number, since it uses as much as digits as its factorization.

1216021541 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 173717370.

The product of its (nonzero) digits is 480, while the sum is 23.

The square root of 1216021541 is about 34871.5004122277. The cubic root of 1216021541 is about 1067.3669620875.

Adding to 1216021541 its reverse (1451206121), we get a palindrome (2667227662).

The spelling of 1216021541 in words is "one billion, two hundred sixteen million, twenty-one thousand, five hundred forty-one".