21019990 has 32 divisors (see below), whose sum is σ = 40738464. Its totient is φ = 7779840.

The previous prime is 21019987. The next prime is 21019993. The reversal of 21019990 is 9991012.

It is an interprime number because it is at equal distance from previous prime (21019987) and next prime (21019993).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21019993) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9357 + ... + 11383.

It is an arithmetic number, because the mean of its divisors is an integer number (1273077).

Almost surely, 2^21019990 is an apocalyptic number.

21019990 is a deficient number, since it is larger than the sum of its proper divisors (19718474).

21019990 is a wasteful number, since it uses less digits than its factorization.

21019990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2112.

The product of its (nonzero) digits is 1458, while the sum is 31.

The square root of 21019990 is about 4584.7562639687. The cubic root of 21019990 is about 275.9799309779.

The spelling of 21019990 in words is "twenty-one million, nineteen thousand, nine hundred ninety".