1621604401 has 4 divisors (see below), whose sum is σ = 1621726704. Its totient is φ = 1621482100.

The previous prime is 1621604371. The next prime is 1621604423. The reversal of 1621604401 is 1044061261.

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: 1044061261 = 199 ⋅5246539.

It is a cyclic number.

It is not a de Polignac number, because 1621604401 - 2²⁷ = 1487386673 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1621604431) 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, 38455 + ... + 68716.

It is an arithmetic number, because the mean of its divisors is an integer number (405431676).

Almost surely, 2^1621604401 is an apocalyptic number.

It is an amenable number.

1621604401 is a deficient number, since it is larger than the sum of its proper divisors (122303).

1621604401 is a wasteful number, since it uses less digits than its factorization.

1621604401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 122302.

The product of its (nonzero) digits is 1152, while the sum is 25.

The square root of 1621604401 is about 40269.1494943710. The cubic root of 1621604401 is about 1174.8478815597.

Adding to 1621604401 its reverse (1044061261), we get a palindrome (2665665662).

The spelling of 1621604401 in words is "one billion, six hundred twenty-one million, six hundred four thousand, four hundred one".