21494987 has 4 divisors (see below), whose sum is σ = 22759416. Its totient is φ = 20230560.

The previous prime is 21494959. The next prime is 21494999. The reversal of 21494987 is 78949412.

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 21494987 - 2¹⁶ = 21429451 is a prime.

It is a super-2 number, since 2×21494987² = 924068932260338, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21494917) 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, 632189 + ... + 632222.

It is an arithmetic number, because the mean of its divisors is an integer number (5689854).

Almost surely, 2^21494987 is an apocalyptic number.

21494987 is a deficient number, since it is larger than the sum of its proper divisors (1264429).

21494987 is a wasteful number, since it uses less digits than its factorization.

21494987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1264428.

The product of its digits is 145152, while the sum is 44.

The square root of 21494987 is about 4636.2686505422. The cubic root of 21494987 is about 278.0432751844.

The spelling of 21494987 in words is "twenty-one million, four hundred ninety-four thousand, nine hundred eighty-seven".