1000156021 has 4 divisors (see below), whose sum is σ = 1000684044. Its totient is φ = 999628000.

The previous prime is 1000155997. The next prime is 1000156043. The reversal of 1000156021 is 1206510001.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 57972996 + 942183025 = 7614^2 + 30695^2 .

It is a cyclic number.

It is not a de Polignac number, because 1000156021 - 2¹³ = 1000147829 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1000155986 and 1000156004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1000156051) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 261160 + ... + 264961.

It is an arithmetic number, because the mean of its divisors is an integer number (250171011).

Almost surely, 2^1000156021 is an apocalyptic number.

It is an amenable number.

1000156021 is a deficient number, since it is larger than the sum of its proper divisors (528023).

1000156021 is an equidigital number, since it uses as much as digits as its factorization.

1000156021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 528022.

The product of its (nonzero) digits is 60, while the sum is 16.

The square root of 1000156021 is about 31625.2434140830. The cubic root of 1000156021 is about 1000.0520042955.

Adding to 1000156021 its reverse (1206510001), we get a palindrome (2206666022).

It can be divided in two parts, 10001560 and 21, that multiplied together give a triangular number (210032760 = T₂₀₄₉₅).

The spelling of 1000156021 in words is "one billion, one hundred fifty-six thousand, twenty-one".