30978921 has 4 divisors (see below), whose sum is σ = 41305232. Its totient is φ = 20652612.

The previous prime is 30978919. The next prime is 30978923. The reversal of 30978921 is 12987903.

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: 12987903 = 3 ⋅4329301.

It is an interprime number because it is at equal distance from previous prime (30978919) and next prime (30978923).

It is not a de Polignac number, because 30978921 - 2¹ = 30978919 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 30978921.

It is not an unprimeable number, because it can be changed into a prime (30978923) 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, 5163151 + ... + 5163156.

It is an arithmetic number, because the mean of its divisors is an integer number (10326308).

Almost surely, 2^30978921 is an apocalyptic number.

It is an amenable number.

30978921 is a deficient number, since it is larger than the sum of its proper divisors (10326311).

30978921 is a wasteful number, since it uses less digits than its factorization.

30978921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10326310.

The product of its (nonzero) digits is 27216, while the sum is 39.

The square root of 30978921 is about 5565.8710908536. The cubic root of 30978921 is about 314.0668478446.

The spelling of 30978921 in words is "thirty million, nine hundred seventy-eight thousand, nine hundred twenty-one".