21701563 has 4 divisors (see below), whose sum is σ = 23370928. Its totient is φ = 20032200.

The previous prime is 21701551. The next prime is 21701609. The reversal of 21701563 is 36510712.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21701563 - 2⁵ = 21701531 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21702563) 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, 834663 + ... + 834688.

It is an arithmetic number, because the mean of its divisors is an integer number (5842732).

Almost surely, 2^21701563 is an apocalyptic number.

21701563 is a deficient number, since it is larger than the sum of its proper divisors (1669365).

21701563 is a wasteful number, since it uses less digits than its factorization.

21701563 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1669364.

The product of its (nonzero) digits is 1260, while the sum is 25.

The square root of 21701563 is about 4658.4936406525. The cubic root of 21701563 is about 278.9311418222.

It can be divided in two parts, 2170 and 1563, that multiplied together give a triangular number (3391710 = T₂₆₀₄).

The spelling of 21701563 in words is "twenty-one million, seven hundred one thousand, five hundred sixty-three".