21513779 has 8 divisors (see below), whose sum is σ = 24713568. Its totient is φ = 18345600.

The previous prime is 21513773. The next prime is 21513787. The reversal of 21513779 is 97731512.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21513779 - 2⁸ = 21513523 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21513773) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6422 + ... + 9179.

It is an arithmetic number, because the mean of its divisors is an integer number (3089196).

Almost surely, 2^21513779 is an apocalyptic number.

21513779 is a deficient number, since it is larger than the sum of its proper divisors (3199789).

21513779 is a wasteful number, since it uses less digits than its factorization.

21513779 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15805.

The product of its digits is 13230, while the sum is 35.

The square root of 21513779 is about 4638.2948375454. The cubic root of 21513779 is about 278.1242780607.

The spelling of 21513779 in words is "twenty-one million, five hundred thirteen thousand, seven hundred seventy-nine".