1216629821 has 4 divisors (see below), whose sum is σ = 1327232544. Its totient is φ = 1106027100.

The previous prime is 1216629809. The next prime is 1216629863. The reversal of 1216629821 is 1289266121.

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 a cyclic number.

It is not a de Polignac number, because 1216629821 - 2¹⁰ = 1216628797 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1216629221) 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, 55301345 + ... + 55301366.

It is an arithmetic number, because the mean of its divisors is an integer number (331808136).

Almost surely, 2^1216629821 is an apocalyptic number.

1216629821 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1216629821 is a deficient number, since it is larger than the sum of its proper divisors (110602723).

1216629821 is a wasteful number, since it uses less digits than its factorization.

1216629821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 110602722.

The product of its digits is 20736, while the sum is 38.

The square root of 1216629821 is about 34880.2210572124. The cubic root of 1216629821 is about 1067.5449056865.

The spelling of 1216629821 in words is "one billion, two hundred sixteen million, six hundred twenty-nine thousand, eight hundred twenty-one".