21011994 has 16 divisors (see below), whose sum is σ = 46693440. Its totient is φ = 7003980.

The previous prime is 21011981. The next prime is 21012053. The reversal of 21011994 is 49911012.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 194502 + ... + 194609.

It is an arithmetic number, because the mean of its divisors is an integer number (2918340).

Almost surely, 2^21011994 is an apocalyptic number.

21011994 is an abundant number, since it is smaller than the sum of its proper divisors (25681446).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21011994 is a wasteful number, since it uses less digits than its factorization.

21011994 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 389122 (or 389116 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 27.

The square root of 21011994 is about 4583.8841608400. The cubic root of 21011994 is about 275.9449323028.

It can be divided in two parts, 2101 and 1994, that added together give a triangular number (4095 = T₉₀).

The spelling of 21011994 in words is "twenty-one million, eleven thousand, nine hundred ninety-four".