21019890 has 32 divisors (see below), whose sum is σ = 53104320. Its totient is φ = 5310144.

The previous prime is 21019879. The next prime is 21019903. The reversal of 21019890 is 9891012.

It is a super-2 number, since 2×21019890² = 883671551224200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17869 + ... + 19008.

It is an arithmetic number, because the mean of its divisors is an integer number (1659510).

Almost surely, 2^21019890 is an apocalyptic number.

21019890 is an abundant number, since it is smaller than the sum of its proper divisors (32084430).

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

21019890 is a wasteful number, since it uses less digits than its factorization.

21019890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36906.

The product of its (nonzero) digits is 1296, while the sum is 30.

The square root of 21019890 is about 4584.7453582506. The cubic root of 21019890 is about 275.9794933304.

It can be divided in two parts, 210 and 19890, that added together give a triangular number (20100 = T₂₀₀).

The spelling of 21019890 in words is "twenty-one million, nineteen thousand, eight hundred ninety".