820021051 has 4 divisors (see below), whose sum is σ = 839091352. Its totient is φ = 800950752.

The previous prime is 820021049. The next prime is 820021067. The reversal of 820021051 is 150120028.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 820021051 - 2¹ = 820021049 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (820021651) 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, 9535086 + ... + 9535171.

It is an arithmetic number, because the mean of its divisors is an integer number (209772838).

Almost surely, 2^820021051 is an apocalyptic number.

820021051 is a deficient number, since it is larger than the sum of its proper divisors (19070301).

820021051 is a wasteful number, since it uses less digits than its factorization.

820021051 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19070300.

The product of its (nonzero) digits is 160, while the sum is 19.

The square root of 820021051 is about 28636.0096905976. The cubic root of 820021051 is about 935.9981718102.

Adding to 820021051 its reverse (150120028), we get a palindrome (970141079).

The spelling of 820021051 in words is "eight hundred twenty million, twenty-one thousand, fifty-one".