21690542 has 4 divisors (see below), whose sum is σ = 32535816. Its totient is φ = 10845270.

The previous prime is 21690527. The next prime is 21690553. The reversal of 21690542 is 24509612.

It is a happy number.

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

It is a super-2 number, since 2×21690542² = 940959224507528, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5422634 + ... + 5422637.

It is an arithmetic number, because the mean of its divisors is an integer number (8133954).

Almost surely, 2^21690542 is an apocalyptic number.

21690542 is a deficient number, since it is larger than the sum of its proper divisors (10845274).

21690542 is a wasteful number, since it uses less digits than its factorization.

21690542 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10845273.

The product of its (nonzero) digits is 4320, while the sum is 29.

The square root of 21690542 is about 4657.3105973298. The cubic root of 21690542 is about 278.8839160279.

The spelling of 21690542 in words is "twenty-one million, six hundred ninety thousand, five hundred forty-two".