21395081 has 4 divisors (see below), whose sum is σ = 21584532. Its totient is φ = 21205632.

The previous prime is 21395063. The next prime is 21395089. The reversal of 21395081 is 18059312.

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

It can be written as a sum of positive squares in 2 ways, for example, as 2175625 + 19219456 = 1475^2 + 4384^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21395081 is a prime.

It is a super-2 number, since 2×21395081² = 915498981993122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21395089) 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, 94556 + ... + 94781.

It is an arithmetic number, because the mean of its divisors is an integer number (5396133).

Almost surely, 2^21395081 is an apocalyptic number.

It is an amenable number.

21395081 is a deficient number, since it is larger than the sum of its proper divisors (189451).

21395081 is a wasteful number, since it uses less digits than its factorization.

21395081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 189450.

The product of its (nonzero) digits is 2160, while the sum is 29.

The square root of 21395081 is about 4625.4817046444. The cubic root of 21395081 is about 277.6118359929.

It can be divided in two parts, 21 and 395081, that multiplied together give a triangular number (8296701 = T₄₀₇₃).

The spelling of 21395081 in words is "twenty-one million, three hundred ninety-five thousand, eighty-one".