1621378819 has 4 divisors (see below), whose sum is σ = 1627687944. Its totient is φ = 1615069696.

The previous prime is 1621378817. The next prime is 1621378831. The reversal of 1621378819 is 9188731261.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 1621378819 - 2¹ = 1621378817 is a prime.

It is a super-2 number, since 2×1621378819² = 5257738549403669522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1621378817) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3154177 + ... + 3154690.

It is an arithmetic number, because the mean of its divisors is an integer number (406921986).

Almost surely, 2^1621378819 is an apocalyptic number.

1621378819 is a deficient number, since it is larger than the sum of its proper divisors (6309125).

1621378819 is an equidigital number, since it uses as much as digits as its factorization.

1621378819 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6309124.

The product of its digits is 145152, while the sum is 46.

The square root of 1621378819 is about 40266.3484686655. The cubic root of 1621378819 is about 1174.7934011893.

The spelling of 1621378819 in words is "one billion, six hundred twenty-one million, three hundred seventy-eight thousand, eight hundred nineteen".