21513847 has 4 divisors (see below), whose sum is σ = 21523320. Its totient is φ = 21504376.

The previous prime is 21513799. The next prime is 21513851. The reversal of 21513847 is 74831512.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21513847 - 2¹⁵ = 21481079 is a prime.

It is a super-2 number, since 2×21513847² = 925691225478818, which contains 22 as substring.

It is a Duffinian number.

It is a zygodrome in base 3.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21513887) 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, 933 + ... + 6625.

It is an arithmetic number, because the mean of its divisors is an integer number (5380830).

Almost surely, 2^21513847 is an apocalyptic number.

21513847 is a deficient number, since it is larger than the sum of its proper divisors (9473).

21513847 is an equidigital number, since it uses as much as digits as its factorization.

21513847 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9472.

The product of its digits is 6720, while the sum is 31.

The square root of 21513847 is about 4638.3021678196. The cubic root of 21513847 is about 278.1245710888.

The spelling of 21513847 in words is "twenty-one million, five hundred thirteen thousand, eight hundred forty-seven".