128431421 has 4 divisors (see below), whose sum is σ = 129678432. Its totient is φ = 127184412.

The previous prime is 128431399. The next prime is 128431423. The reversal of 128431421 is 124134821.

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: 124134821 = 73 ⋅1700477.

It is a cyclic number.

It is not a de Polignac number, because 128431421 - 2¹⁸ = 128169277 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128431423) 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, 623351 + ... + 623556.

It is an arithmetic number, because the mean of its divisors is an integer number (32419608).

Almost surely, 2^128431421 is an apocalyptic number.

It is an amenable number.

128431421 is a deficient number, since it is larger than the sum of its proper divisors (1247011).

128431421 is a wasteful number, since it uses less digits than its factorization.

128431421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1247010.

The product of its digits is 1536, while the sum is 26.

The square root of 128431421 is about 11332.7587550428. The cubic root of 128431421 is about 504.5339896026.

The spelling of 128431421 in words is "one hundred twenty-eight million, four hundred thirty-one thousand, four hundred twenty-one".