21309799 has 16 divisors (see below), whose sum is σ = 25671168. Its totient is φ = 17294112.

The previous prime is 21309793. The next prime is 21309829. The reversal of 21309799 is 99790312.

21309799 = 658² + 659² + ... + 703².

It is a cyclic number.

It is not a de Polignac number, because 21309799 - 2⁷ = 21309671 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21309793) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16609 + ... + 17845.

It is an arithmetic number, because the mean of its divisors is an integer number (1604448).

Almost surely, 2^21309799 is an apocalyptic number.

21309799 is a deficient number, since it is larger than the sum of its proper divisors (4361369).

21309799 is a wasteful number, since it uses less digits than its factorization.

21309799 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1374.

The product of its (nonzero) digits is 30618, while the sum is 40.

The square root of 21309799 is about 4616.2537841847. The cubic root of 21309799 is about 277.2424859935.

The spelling of 21309799 in words is "twenty-one million, three hundred nine thousand, seven hundred ninety-nine".