78129421 has 4 divisors (see below), whose sum is σ = 78161344. Its totient is φ = 78097500.

The previous prime is 78129419. The next prime is 78129431. The reversal of 78129421 is 12492187.

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.

It is a cyclic number.

It is not a de Polignac number, because 78129421 - 2¹ = 78129419 is a prime.

It is a super-2 number, since 2×78129421² = 12208412851590482, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78129431) 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, 11955 + ... + 17296.

It is an arithmetic number, because the mean of its divisors is an integer number (19540336).

Almost surely, 2^78129421 is an apocalyptic number.

It is an amenable number.

78129421 is a deficient number, since it is larger than the sum of its proper divisors (31923).

78129421 is a wasteful number, since it uses less digits than its factorization.

78129421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31922.

The product of its digits is 8064, while the sum is 34.

The square root of 78129421 is about 8839.0848508202. The cubic root of 78129421 is about 427.5020503076.

The spelling of 78129421 in words is "seventy-eight million, one hundred twenty-nine thousand, four hundred twenty-one".