78045721 has 12 divisors (see below), whose sum is σ = 84768528. Its totient is φ = 71823024.

The previous prime is 78045713. The next prime is 78045743. The reversal of 78045721 is 12754087.

It is a happy number.

It is not a de Polignac number, because 78045721 - 2³ = 78045713 is a prime.

It is a super-2 number, since 2×78045721² = 12182269132819682, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (78045701) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 87946 + ... + 88828.

It is an arithmetic number, because the mean of its divisors is an integer number (7064044).

Almost surely, 2^78045721 is an apocalyptic number.

It is an amenable number.

78045721 is a deficient number, since it is larger than the sum of its proper divisors (6722807).

78045721 is a wasteful number, since it uses less digits than its factorization.

78045721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1432 (or 1419 counting only the distinct ones).

The product of its (nonzero) digits is 15680, while the sum is 34.

The square root of 78045721 is about 8834.3489290383. The cubic root of 78045721 is about 427.3493348667.

The spelling of 78045721 in words is "seventy-eight million, forty-five thousand, seven hundred twenty-one".