21019761 has 12 divisors (see below), whose sum is σ = 34699392. Its totient is φ = 12011256.

The previous prime is 21019729. The next prime is 21019771. The reversal of 21019761 is 16791012.

It is not a de Polignac number, because 21019761 - 2⁵ = 21019729 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21019771) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 166761 + ... + 166886.

It is an arithmetic number, because the mean of its divisors is an integer number (2891616).

Almost surely, 2^21019761 is an apocalyptic number.

21019761 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21019761 is a deficient number, since it is larger than the sum of its proper divisors (13679631).

21019761 is a wasteful number, since it uses less digits than its factorization.

21019761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 333660 (or 333657 counting only the distinct ones).

The product of its (nonzero) digits is 756, while the sum is 27.

The square root of 21019761 is about 4584.7312898359. The cubic root of 21019761 is about 275.9789287631.

The spelling of 21019761 in words is "twenty-one million, nineteen thousand, seven hundred sixty-one".