1211012820 has 36 divisors (see below), whose sum is σ = 3673406100. Its totient is φ = 322936704.

The previous prime is 1211012807. The next prime is 1211012821. The reversal of 1211012820 is 282101121.

It can be written as a sum of positive squares in 2 ways, for example, as 819447876 + 391564944 = 28626^2 + 19788^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 1211012793 and 1211012802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1211012821) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3363745 + ... + 3364104.

Almost surely, 2^1211012820 is an apocalyptic number.

1211012820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1211012820 is an abundant number, since it is smaller than the sum of its proper divisors (2462393280).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1211012820 is a wasteful number, since it uses less digits than its factorization.

1211012820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6727864 (or 6727859 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 18.

The square root of 1211012820 is about 34799.6094805675. The cubic root of 1211012820 is about 1065.8994715512.

Adding to 1211012820 its reverse (282101121), we get a palindrome (1493113941).

The spelling of 1211012820 in words is "one billion, two hundred eleven million, twelve thousand, eight hundred twenty".