21531963 has 16 divisors (see below), whose sum is σ = 29505056. Its totient is φ = 13962240.

The previous prime is 21531953. The next prime is 21531967. The reversal of 21531963 is 36913512.

It is not a de Polignac number, because 21531963 - 2⁴ = 21531947 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21531963.

It is not an unprimeable number, because it can be changed into a prime (21531967) 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, 17145 + ... + 18357.

It is an arithmetic number, because the mean of its divisors is an integer number (1844066).

Almost surely, 2^21531963 is an apocalyptic number.

21531963 is a deficient number, since it is larger than the sum of its proper divisors (7973093).

21531963 is a wasteful number, since it uses less digits than its factorization.

21531963 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 digits is 4860, while the sum is 30.

The square root of 21531963 is about 4640.2546266342. The cubic root of 21531963 is about 278.2026152611.

The spelling of 21531963 in words is "twenty-one million, five hundred thirty-one thousand, nine hundred sixty-three".