21019931 has 8 divisors (see below), whose sum is σ = 21471840. Its totient is φ = 20572992.

The previous prime is 21019927. The next prime is 21019937. The reversal of 21019931 is 13991012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21019931 - 2² = 21019927 is a prime.

It is a super-2 number, since 2×21019931² = 883674998489522, which contains 22 as substring.

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 21019931.

It is not an unprimeable number, because it can be changed into a prime (21019937) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8021 + ... + 10313.

It is an arithmetic number, because the mean of its divisors is an integer number (2683980).

Almost surely, 2^21019931 is an apocalyptic number.

21019931 is a deficient number, since it is larger than the sum of its proper divisors (451909).

21019931 is a wasteful number, since it uses less digits than its factorization.

21019931 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2485.

The product of its (nonzero) digits is 486, while the sum is 26.

The square root of 21019931 is about 4584.7498295981. The cubic root of 21019931 is about 275.9796727661.

The spelling of 21019931 in words is "twenty-one million, nineteen thousand, nine hundred thirty-one".