1621261673 has 4 divisors (see below), whose sum is σ = 1622512980. Its totient is φ = 1620010368.

The previous prime is 1621261669. The next prime is 1621261687. The reversal of 1621261673 is 3761621261.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 3761621261 = 79 ⋅47615459.

It can be written as a sum of positive squares in 2 ways, for example, as 1067459584 + 553802089 = 32672^2 + 23533^2 .

It is a cyclic number.

It is not a de Polignac number, because 1621261673 - 2² = 1621261669 is a prime.

It is a super-3 number, since 3×1621261673³ (a number of 29 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1621261643) 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, 623708 + ... + 626301.

It is an arithmetic number, because the mean of its divisors is an integer number (405628245).

Almost surely, 2^1621261673 is an apocalyptic number.

It is an amenable number.

1621261673 is a deficient number, since it is larger than the sum of its proper divisors (1251307).

1621261673 is a wasteful number, since it uses less digits than its factorization.

1621261673 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1251306.

The product of its digits is 18144, while the sum is 35.

The square root of 1621261673 is about 40264.8938034114. The cubic root of 1621261673 is about 1174.7651072334.

The spelling of 1621261673 in words is "one billion, six hundred twenty-one million, two hundred sixty-one thousand, six hundred seventy-three".