21771631 has 12 divisors (see below), whose sum is σ = 25917672. Its totient is φ = 18225648.

The previous prime is 21771619. The next prime is 21771671. The reversal of 21771631 is 13617712.

It is not a de Polignac number, because 21771631 - 2¹³ = 21763439 is a prime.

It is a super-2 number, since 2×21771631² = 948007832800322, which contains 22 as substring.

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 21771631.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21771671) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3060 + ... + 7273.

It is an arithmetic number, because the mean of its divisors is an integer number (2159806).

Almost surely, 2^21771631 is an apocalyptic number.

21771631 is a deficient number, since it is larger than the sum of its proper divisors (4146041).

21771631 is a wasteful number, since it uses less digits than its factorization.

21771631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10390 (or 10383 counting only the distinct ones).

The product of its digits is 1764, while the sum is 28.

The square root of 21771631 is about 4666.0080368555. The cubic root of 21771631 is about 279.2310150123.

The spelling of 21771631 in words is "twenty-one million, seven hundred seventy-one thousand, six hundred thirty-one".