21060781 has 4 divisors (see below), whose sum is σ = 24069472. Its totient is φ = 18052092.

The previous prime is 21060763. The next prime is 21060829. The reversal of 21060781 is 18706012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21060781 - 2⁹ = 21060269 is a prime.

It is a super-2 number, since 2×21060781² = 887112992659922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21060701) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1504335 + ... + 1504348.

It is an arithmetic number, because the mean of its divisors is an integer number (6017368).

Almost surely, 2^21060781 is an apocalyptic number.

It is an amenable number.

21060781 is a deficient number, since it is larger than the sum of its proper divisors (3008691).

21060781 is an equidigital number, since it uses as much as digits as its factorization.

21060781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3008690.

The product of its (nonzero) digits is 672, while the sum is 25.

The square root of 21060781 is about 4589.2026540566. The cubic root of 21060781 is about 276.1583361242.

Adding to 21060781 its reverse (18706012), we get a palindrome (39766793).

The spelling of 21060781 in words is "twenty-one million, sixty thousand, seven hundred eighty-one".