21917679 has 16 divisors (see below), whose sum is σ = 33725952. Its totient is φ = 12401568.

The previous prime is 21917677. The next prime is 21917683. The reversal of 21917679 is 97671912.

It is a happy number.

It is not a de Polignac number, because 21917679 - 2¹ = 21917677 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21917679.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21917677) 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, 2904 + ... + 7229.

It is an arithmetic number, because the mean of its divisors is an integer number (2107872).

Almost surely, 2^21917679 is an apocalyptic number.

21917679 is a deficient number, since it is larger than the sum of its proper divisors (11808273).

21917679 is a wasteful number, since it uses less digits than its factorization.

21917679 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10246.

The product of its digits is 47628, while the sum is 42.

The square root of 21917679 is about 4681.6320872106. The cubic root of 21917679 is about 279.8540012669.

It can be divided in two parts, 2191 and 7679, that added together give a triangular number (9870 = T₁₄₀).

The spelling of 21917679 in words is "twenty-one million, nine hundred seventeen thousand, six hundred seventy-nine".