3638869921 has 4 divisors (see below), whose sum is σ = 3641410692. Its totient is φ = 3636329152.

The previous prime is 3638869903. The next prime is 3638869933. The reversal of 3638869921 is 1299688363.

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

It can be written as a sum of positive squares in 2 ways, for example, as 2721082896 + 917787025 = 52164^2 + 30295^2 .

It is a cyclic number.

It is not a de Polignac number, because 3638869921 - 2¹³ = 3638861729 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (3638869901) 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, 1268236 + ... + 1271101.

It is an arithmetic number, because the mean of its divisors is an integer number (910352673).

Almost surely, 2^3638869921 is an apocalyptic number.

It is an amenable number.

3638869921 is a deficient number, since it is larger than the sum of its proper divisors (2540771).

3638869921 is a wasteful number, since it uses less digits than its factorization.

3638869921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2540770.

The product of its digits is 3359232, while the sum is 55.

The square root of 3638869921 is about 60323.0463504621. The cubic root of 3638869921 is about 1538.1151281877.

The spelling of 3638869921 in words is "three billion, six hundred thirty-eight million, eight hundred sixty-nine thousand, nine hundred twenty-one".