78221421 has 6 divisors (see below), whose sum is σ = 112986510. Its totient is φ = 52147608.

The previous prime is 78221419. The next prime is 78221447. The reversal of 78221421 is 12412287.

It can be written as a sum of positive squares in only one way, i.e., 47817225 + 30404196 = 6915^2 + 5514^2 .

It is not a de Polignac number, because 78221421 - 2¹ = 78221419 is a prime.

It is a super-2 number, since 2×78221421² = 12237181406518482, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78221621) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4345626 + ... + 4345643.

It is an arithmetic number, because the mean of its divisors is an integer number (18831085).

Almost surely, 2^78221421 is an apocalyptic number.

It is an amenable number.

78221421 is a deficient number, since it is larger than the sum of its proper divisors (34765089).

78221421 is a wasteful number, since it uses less digits than its factorization.

78221421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8691275 (or 8691272 counting only the distinct ones).

The product of its digits is 1792, while the sum is 27.

The square root of 78221421 is about 8844.2874783670. The cubic root of 78221421 is about 427.6697837969.

The spelling of 78221421 in words is "seventy-eight million, two hundred twenty-one thousand, four hundred twenty-one".