1220400021 has 4 divisors (see below), whose sum is σ = 1627200032. Its totient is φ = 813600012.

The previous prime is 1220400019. The next prime is 1220400031. The reversal of 1220400021 is 1200040221.

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.

It is not a de Polignac number, because 1220400021 - 2¹ = 1220400019 is a prime.

It is a super-2 number, since 2×1220400021² = 2978752422513600882, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1220400031) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 203400001 + ... + 203400006.

It is an arithmetic number, because the mean of its divisors is an integer number (406800008).

Almost surely, 2^1220400021 is an apocalyptic number.

It is an amenable number.

1220400021 is a deficient number, since it is larger than the sum of its proper divisors (406800011).

1220400021 is an equidigital number, since it uses as much as digits as its factorization.

1220400021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 406800010.

The product of its (nonzero) digits is 32, while the sum is 12.

The square root of 1220400021 is about 34934.2242077880. The cubic root of 1220400021 is about 1068.6465027235.

Adding to 1220400021 its reverse (1200040221), we get a palindrome (2420440242).

The spelling of 1220400021 in words is "one billion, two hundred twenty million, four hundred thousand, twenty-one".