1211000021 has 16 divisors (see below), whose sum is σ = 1538310528. Its totient is φ = 925828800.

The previous prime is 1210999987. The next prime is 1211000023. The reversal of 1211000021 is 1200001121.

It is a cyclic number.

It is not a de Polignac number, because 1211000021 - 2¹⁸ = 1210737877 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 1210999972 and 1211000008.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1211000023) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 144290 + ... + 152451.

It is an arithmetic number, because the mean of its divisors is an integer number (96144408).

Almost surely, 2^1211000021 is an apocalyptic number.

1211000021 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1211000021 is a deficient number, since it is larger than the sum of its proper divisors (327310507).

1211000021 is a wasteful number, since it uses less digits than its factorization.

1211000021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 296812.

The product of its (nonzero) digits is 4, while the sum is 8.

The square root of 1211000021 is about 34799.4255843398. The cubic root of 1211000021 is about 1065.8957164312.

Adding to 1211000021 its reverse (1200001121), we get a palindrome (2411001142).

The spelling of 1211000021 in words is "one billion, two hundred eleven million, twenty-one", and thus it is an aban number.