1021000021 has 4 divisors (see below), whose sum is σ = 1021416352. Its totient is φ = 1020583692.

The previous prime is 1021000009. The next prime is 1021000027. The reversal of 1021000021 is 1200001201.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1200001201 = 7 ⋅171428743.

It is a cyclic number.

It is not a de Polignac number, because 1021000021 - 2⁵ = 1020999989 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1020999968 and 1021000013.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1021000027) 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, 204465 + ... + 209398.

It is an arithmetic number, because the mean of its divisors is an integer number (255354088).

Almost surely, 2^1021000021 is an apocalyptic number.

It is an amenable number.

1021000021 is a deficient number, since it is larger than the sum of its proper divisors (416331).

1021000021 is an equidigital number, since it uses as much as digits as its factorization.

1021000021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 416330.

The product of its (nonzero) digits is 4, while the sum is 7.

The square root of 1021000021 is about 31953.0909459476. The cubic root of 1021000021 is about 1006.9515706883.

Adding to 1021000021 its reverse (1200001201), we get a palindrome (2221001222).

The spelling of 1021000021 in words is "one billion, twenty-one million, twenty-one", and thus it is an aban number and an uban number.